Method and apparatus for performing device-to-device communication

ABSTRACT

A method and apparatus for performing Device-to-Device (D2D) communication are provided. The method includes being assigned a transmission and reception indicator and an index during D2D connection setup between a User Equipment (UE) and a Base Station (BS) by the UE, the transmission and reception indicator indicating a transmission role or a reception role and the index indicating another UE for D2D communication, receiving the transmission and reception indicator, the index, and resource information for the D2D communication on a control channel by the UE, and performing, by the UE, a transmission operation or a reception operation to or from the other UE indicated by the index in resources indicated by the resource information according to the transmission role or the reception role indicated by the transmission and reception indicator.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under 35 U.S.C. §119(a) of an Indiapatent application filed on Jun. 28, 2013 in the Indian IntellectualProperty Office and assigned Serial No. IN 782/KOL/2013, and of a Koreanpatent application filed on Jun. 27, 2014 in the Korean IntellectualProperty Office and assigned Serial No. 10-2014-0079486, the entiredisclosure of each of which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a method and apparatus for allocatingresources and performing communication in a Device-to-Device (D2D)communication system.

BACKGROUND

The recent proliferation of smartphones is a driving force behind therapid growth of data traffic. According to the Korea CommunicationsCommittee, it was reported in 2013 that, due to the increasingpopularity of smartphones, mobile data traffic had tripled since thelast estimate. Considering that the number of smartphone users will befurther increasing and more application services will be used insmartphones, it is expected that mobile data traffic will also beincreasing. Particularly, if Machine-to-Machine (M2M) communicationincluding communication between a person and a thing, communicationbetween things, and the like is boosted as a new mobile market beyondcommunication between humans, the traffic transmitted to a Base Station(BS) will be exceedingly large.

Accordingly, there is a need address these problems. In this context,Device-to-Device (D2D) communication has recently attracted muchattention and research on resource allocation for D2D communication isunderway.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method and apparatus for efficientlyallocating resources for Device-to-Device (D2D) communication.

Another aspect of the present disclosure is to provide a method andapparatus for allocating transmission resources and reception resourcesfor D2D communication to a User Equipment (UE) and enabling the UE toidentify the allocated transmission resources and reception resources.

In accordance with an aspect of the present disclosure, a method andapparatus for performing D2D communication is provided. The methodincludes being assigned a transmission and reception indicator and anindex during D2D connection setup between a UE and a Base Station (BS)by the UE, the transmission and reception indicator indicating atransmission role or a reception role and the index indicating anotherUE for D2D communication, receiving the transmission and receptionindicator, the index, and resource information for the D2D communicationon a control channel by the UE, and performing, by the UE, atransmission operation or a reception operation to or from the other UEindicated by the index in resources indicated by the resourceinformation according to the transmission role or the reception roleindicated by the transmission and reception indicator.

In accordance with another aspect of the present disclosure, a methodfor performing D2D communication is provided. The method includesassigning a transmission and reception indicator and an index to a UEduring D2D connection setup between the UE and a BS by the BS, thetransmission and reception indicator indicating a transmission role or areception role and the index indicating another UE for D2Dcommunication, and transmitting the transmission and receptionindicator, the index, and resource information for the D2D communicationon a control channel to the UE by the BS. The D2D communication isperformed between the UE and the other UE by performing a transmissionoperation or a reception operation between the UE and the other UEindicated by the index in resources indicated by the resourceinformation according to the transmission role or the reception roleindicated by the transmission and reception indicator.

In accordance with another aspect of the present disclosure, a UE forperforming D2D is provided. The UE includes a transceiver configured toperform D2D communication with another UE through a direct communicationlink, and a controller configured to control a transmission andreception indicator and an index to be assigned during D2D connectionsetup between the UE and a BS, and to control the transmission andreception indicator indicating a transmission role or a reception roleand the index indicating the other UE for the D2D communication,reception of the transmission and reception indicator, the index, andresource information for the D2D communication on a control channel, andperforming of a transmission operation or a reception operation to orfrom the other UE indicated by the index in resources indicated by theresource information according to the transmission role or the receptionrole indicated by the transmission and reception indicator.

In accordance with another aspect of the present disclosure, a BS forperforming D2D communication is provided. The BS includes a controllerconfigured to control assignment of a transmission and receptionindicator and an index to a UE during D2D connection setup between theUE and the BS, the transmission and reception indicator indicating atransmission role or a reception role and the index indicating anotherUE for D2D communication, and transmission of the transmission andreception indicator, the index, and resource information for the D2Dcommunication on a control channel to the UE, and a transceiverconfigured to communicate with at least one UE under control of thecontroller. The D2D communication is performed between the UE and theother UE by performing a transmission operation or a reception operationbetween the UE and the other UE determined by the index in resourcesindicated by the resource information according to the transmission roleor the reception role indicated by the transmission and receptionindicator.

In accordance with another aspect of the present disclosure, a methodfor performing D2D communication is provided. The method includes beingassigned a network temporary ID for D2D communication during D2Dconnection setup with a BS by a UE, receiving resource information forthe D2D communication on a control channel masked with the networktemporary ID by the UE, and performing a transmission operation or areception operation to or from another UE determined based on thenetwork temporary ID in resources indicated by the resource informationby the UE.

In accordance with another aspect of the present disclosure, a methodfor performing D2D communication is provided. The method includesassigning a network temporary ID for D2D communication to a UE duringD2D connection setup with the UE by a BS, and transmitting resourceinformation for the D2D communication on a control channel masked withthe network temporary ID to the UE by the BS. The D2D communication isperformed between the UE and another UE by a transmission operation or areception operation between the UE and the other UE determined based onthe network temporary ID in resources indicated by the resourceinformation.

In accordance with another aspect of the present disclosure, a UE forperforming D2D communication is provided. The UE includes a transceiverconfigured to perform D2D communication with another UE through a directcommunication link, and a controller configured to control a networktemporary ID for D2D communication to be assigned during D2D connectionsetup with a BS, and to control reception of resource information forthe D2D communication on a control channel masked with the networktemporary ID and performing of a transmission operation or a receptionoperation to or from another UE determined based on the networktemporary ID in resources indicated by the resource information.

In accordance with another aspect of the present disclosure, a BS forperforming D2D communication is provided. The BS includes a controllerconfigured to control assignment of a network temporary ID for D2Dcommunication to a UE during D2D connection setup with the UE andtransmission of resource information for the D2D communication on acontrol channel masked with the network temporary ID to the UE, and atransceiver configured to communicate with at least one UE under controlof the controller. The D2D communication is performed between the UE andanother UE by a transmission operation or a reception operation betweenthe UE and the other UE determined based on the network temporary ID inresources indicated by the resource information.

In accordance with another aspect of the present disclosure, a methodfor performing D2D communication is provided. The method includes beingassigned a UE pair ID for D2D communication during D2D connection setupwith a BS by a UE, receiving the UE pair ID and resource information forthe D2D communication on a control channel by the UE, the controlchannel being masked with a network temporary ID reserved for D2Dcommunication, and performing a transmission operation or a receptionoperation to or from another UE determined based on the UE pair ID inresources indicated by the resource information by the UE. The networktemporary ID is the same for all D2D connections.

In accordance with another aspect of the present disclosure, a methodfor performing D2D communication is provided. The method includesassigning a UE pair ID for D2D communication to a UE during D2Dconnection setup with the UE by a BS, and transmitting the UE pair IDand resource information for the D2D communication on a control channelto the UE by the BS, the control channel being masked with a networktemporary ID reserved for D2D communication. The D2D communication isperformed between the UE and another UE by a transmission operation or areception operation between the UE and the other UE based on the UE pairID in resources indicated by the resource information. The networktemporary ID is the same for all D2D connections.

In accordance with another aspect of the present disclosure, a UE forperforming D2D communication is provided. The UE includes a transceiverconfigured to perform D2D communication with another UE on a directcommunication link, and a controller configured to control a UE pair IDfor D2D communication to be allocated to the UE during D2D connectionsetup with a BS, to control reception of the UE pair ID and resourceinformation for the D2D communication on a control channel, the controlchannel being masked with a network temporary ID reserved for D2Dcommunication, and to control performing of a transmission operation ora reception operation to or from another UE determined based on the UEpair ID in resources indicated by the resource information. The networktemporary ID is the same for all D2D connections.

In accordance with another aspect of the present disclosure, a BS forperforming D2D communication is provided. The BS includes a controllerconfigured to control assignment of a UE pair ID for D2D communicationto a UE during D2D connection setup with the UE, and transmission of theUE pair ID and resource information for the D2D communication on acontrol channel to the UE, the control channel being masked with anetwork temporary ID reserved for D2D communication, and a transceiverconfigured to communicate with at least one UE under control of thecontroller. The D2D communication is performed between the UE andanother UE by a transmission operation or a reception operation betweenthe UE and the other UE based on the UE pair ID in resources indicatedby the resource information. The network temporary ID is the same forall D2D connections.

In accordance with another aspect of the present disclosure, a methodfor performing D2D communication is provided. The method includesreceiving a network temporary ID of another UE for D2D communicationduring D2D connection setup with a BS by a UE, receiving informationabout the other UE and resource information for the D2D communicationwith the other UE on a control channel by the UE, the control channelbeing masked with a network temporary ID of a UE to play a transmissionrole or a reception role in the D2D communication, and performing atransmission operation or a reception operation to or from the other UEbased on the network temporary ID used in masking the control channeland the information about the other UE in resources indicated by theresource information by the UE. The network temporary ID is differentfor each UE.

In accordance with another aspect of the present disclosure, a methodfor performing D2D communication is provided. The method includestransmitting a network temporary ID of another UE for D2D communicationduring D2D connection setup with a UE by a BS, and transmittinginformation about the other UE and resource information for the D2Dcommunication with the other UE on a control channel to the UE by theBS, the control channel being masked with a network temporary ID of a UEto play a transmission role or a reception role in the D2Dcommunication. The D2D communication is performed between the UE and theother UE by a transmission operation or a reception operation betweenthe UE and the other UE based on the network temporary ID used inmasking the control channel and the information about the other UE inresources indicated by the resource information. The network temporaryID is different for each UE.

In accordance with another aspect of the present disclosure, a UE forperforming D2D communication is provided. The UE includes a transceiverconfigured to perform D2D communication with another UE on a directcommunication link, and a controller configured to control reception ofa network temporary ID of the other UE for the D2D communication duringD2D connection setup with a BS, reception of information about the otherUE and resource information for the D2D communication with the other UEon a control channel masked with a network temporary ID of a UE to playa transmission role or a reception role in the D2D communication, andperforming of a transmission operation or a reception operation to orfrom the other UE based on the network temporary ID used in masking thecontrol channel and the information about the other UE in resourcesindicated by the resource information. The network temporary ID isdifferent for each UE.

In accordance with another aspect of the present disclosure, a BS forperforming D2D communication is provided. The BS includes a controllerconfigured to control transmission of a network temporary ID of anotherUE for D2D communication during D2D connection setup with a UE, andtransmission of information about the other UE and resource informationfor the D2D communication with the other UE on a control channel to theUE, the control channel being masked with a network temporary ID of a UEto play a transmission role or a reception role in the D2Dcommunication, and a transceiver configured to communicate with at leastone UE under control of the controller. The D2D communication isperformed between the UE and the other UE by a transmission operation ora reception operation between the UE and the other UE based on thenetwork temporary ID used in masking the control channel and theinformation about the other UE in resources indicated by the resourceinformation. The network temporary ID is different for each UE.

In accordance with another aspect of the present disclosure, a methodfor allocating resources for Device-to-Device (D2D) communication isprovided. The method includes requesting resources for D2D communicationby transmitting a D2D buffer status report or a D2D scheduling requestto a Base Station (BS); and receiving resources for D2D communicationfrom BS, wherein the resources for D2D communication is received on acontrol channel in a downlink (DL) subframe corresponding to an uplink(UL) subframe reserved for D2D communication, or on a control channelusing control information format for D2D communication, or on a controlchannel with Cyclic Redundancy Check (CRC) masked using a radio networkterminal identifier (RNTI) assigned to a User Equipment (UE) for D2Dcommunication.

In accordance with another aspect of the present disclosure, a methodfor allocating resources for Device-to-Device (D2D) communication isproved. The method includes receiving a buffer status report or ascheduling request from a User Equipment (UE); determining whether thebuffer status report or the scheduling request is for D2D communication,allocating resources for D2D communication if the buffer status reportor the scheduling request is for D2D communication and transmitting theallocated resources for D2D communication to the UE, wherein theresources for D2D communication is transmitted on a control channel in adownlink (DL) subframe corresponding to an uplink (UL) subframe reservedfor D2D communication, or on a control channel using control informationformat for D2D communication or on a control channel with CyclicRedundancy Check (CRC) masked using a radio network terminal identifier(RNTI) assigned to a User Equipment (UE) for D2D communication.

In accordance with another aspect of the present disclosure, a UserEquipment (UE) for allocating resources for Device-to-Device (D2D)communication is proved. The UE includes a transceiver configured toperform D2D communication with another UE through a direct communicationlink; and a controller configured to control for requesting resourcesfor D2D communication by transmitting a D2D buffer status report or aD2D scheduling request to a Base Station (BS) and for receivingresources for D2D communication from BS, wherein the resources for D2Dcommunication is received on a control channel in a downlink (DL)subframe corresponding to an uplink (UL) subframe reserved for D2Dcommunication, or on a control channel using control information formatfor D2D communication, or on a control channel with Cyclic RedundancyCheck (CRC) masked using a radio network terminal identifier (RNTI)assigned to a User Equipment (UE) for D2D communication.

In accordance with another aspect of the present disclosure, a BaseStation (BS) for allocating resources for Device-to-Device (D2D)communication is proved. The BS includes a controller configured tocontrol for receiving a buffer status report or a scheduling requestfrom a User Equipment (UE), determining whether the buffer status reportor the scheduling request is for D2D communication, allocating resourcesfor D2D communication if the buffer status report or the schedulingrequest is for D2D communication and transmitting the allocatedresources for D2D communication to the UE and a transceiver configuredto perform communication with the UE by controlling of the controller,wherein the resources for D2D communication is transmitted on a controlchannel in a downlink (DL) subframe corresponding to an uplink (UL)subframe reserved for D2D communication, or on a control channel usingcontrol information format for D2D communication or on a control channelwith Cyclic Redundancy Check (CRC) masked using a radio network terminalidentifier (RNTI) assigned to the UE for D2D communication.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 illustrates a Device-to-Device (D2D) communication environmentaccording to the related art;

FIG. 2 illustrates a case in which a plurality of User Equipment (UE)pairs connected to an evolved Node B (eNB) participate in D2Dcommunication according to an embodiment of the present disclosure;

FIG. 3 illustrates a method for allocating resources for D2Dcommunication according to an embodiment of the present disclosure;

FIG. 4 illustrates another method for allocating resources for D2Dcommunication according to an embodiment of the present disclosure;

FIG. 5 illustrates a third method for allocating resources for D2Dcommunication according to an embodiment of the present disclosure;

FIGS. 6 and 7 illustrate a method for allocating resources for D2Dcommunication between cells according to an embodiment of the presentdisclosure;

FIGS. 8 and 9 illustrate a method for allocating resources for D2Dcommunication within a cell according to an embodiment of the presentdisclosure;

FIG. 10 illustrates a method for allocating a transmission index and areception index in allocating resources for D2D communication betweencells according to an embodiment of the present disclosure;

FIG. 11 illustrates another method for allocating a transmission indexand a reception index in allocating resources for D2D communicationbetween cells according to an embodiment of the present disclosure;

FIG. 12 illustrates a method for allocating a transmission index and areception index in allocating resources for D2D communication within acell according to an embodiment of the present disclosure;

FIG. 13 illustrates another method for allocating a transmission indexand a reception index in allocating resources for D2D communicationwithin a cell according to an embodiment of the present disclosure;

FIGS. 14 and 15 are diagrams illustrating signal flows for allocating aconnection index instead of a Tx index or an Rx index for D2Dcommunication according to an embodiment of the present disclosure;

FIG. 16 illustrates an example of allocating Cell Radio NetworkTemporary Identifiers (C-RNTIs) and UE-pair C-RNTIs according to anembodiment of the present disclosure;

FIG. 17 illustrates an example of reusing a C-RNTI address space forUE-pair C-RNTIs according to an embodiment of the present disclosure;

FIGS. 18A and 18B illustrate methods for allocating resources fortransmission of a D2D Buffer Status Report according to an embodiment ofthe present disclosure;

FIG. 19 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for other UEs within thecoverage area of an eNB according to an embodiment of the presentdisclosure;

FIG. 20 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for communication betweena UE of the UE pair and an eNB according to an embodiment of the presentdisclosure;

FIG. 21 illustrates an example of distinguishing resources forcommunication between one UE pair from resources for communicationbetween another UE pair according to an embodiment of the presentdisclosure;

FIG. 22 illustrates a method for identifying transmission resources andreception resources in the case of unidirectional communicationaccording to an embodiment of the present disclosure;

FIG. 23 illustrates a method for identifying transmission resources andreception resources in the case of bidirectional communication accordingto an embodiment of the present disclosure;

FIG. 24 illustrates a method for identifying transmission resources andreception resources in the case of bidirectional communication accordingto an embodiment of the present disclosure;

FIG. 25 illustrates a method for allocating a UE index (UE_idx) and aUE-pair C-RNTI (C-RNTI_(UE-pair)) in allocating resources for D2Dcommunication within a cell according to an embodiment of the presentdisclosure;

FIG. 26 is a diagram illustrating a signal flow for allocating atransmission UE-pair C-RNTI (Tx C-RNTI_(UE-pair)) and a receptionUE-pair C-RNTI (Rx C-RNTI_(UE-pair)) according to an embodiment of thepresent disclosure;

FIG. 27 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for other UEs within thecoverage area of an eNB according to an embodiment of the presentdisclosure;

FIG. 28 illustrates an example of distinguishing resources for UE paircommunication from resources for communication between the UEs of a UEpair and an eNB according to an embodiment of the present disclosure;

FIG. 29 illustrates an example of distinguishing resources for UE paircommunication from resources for other UE pair communication accordingto an embodiment of the present disclosure;

FIG. 30 illustrates a method for allocating a UE index and a UE pair IDin allocating resources for D2D communication within a cell according toan embodiment of the present disclosure;

FIG. 31 illustrates an operation for allocating a transmission UE pairID and a reception UE pair ID according to an embodiment of the presentdisclosure;

FIG. 32 illustrates a method for using a unified C-RNTI for directcommunication according to an embodiment of the present disclosure;

FIG. 33 illustrates an example of using a unified C-RNTI and atransmission and reception index for direct communication according toan embodiment of the present disclosure;

FIG. 34 is a diagram illustrating a signal flow for allocating atransmission and reception index in allocating resources for D2Dcommunication within a cell according to an embodiment of the presentdisclosure;

FIG. 35 is a diagram illustrating a signal flow for allocatingtransmission and reception indexes to UEs according to an embodiment ofthe present disclosure;

FIG. 36 illustrates an example of distinguishing resources for UE paircommunication from other resources within the coverage area of an eNBaccording to an embodiment of the present disclosure;

FIG. 37 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for communication betweena UE of the UE pair and an eNB according to an embodiment of the presentdisclosure;

FIG. 38 illustrates an example of distinguishing resources forcommunication between one UE pair from resources for communicationbetween another UE according to an embodiment of the present disclosure;

FIG. 39 illustrates a method for using a unified C-RNTI and atransmission and reception index for direct communication according toan embodiment of the present disclosure;

FIG. 40 illustrates an example of distinguishing resources forcommunication between a UE pair from other resources within the coveragearea of an eNB according to an embodiment of the present disclosure;

FIG. 41 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for communication betweenan eNB and a UE of the UE pair according to an embodiment of the presentdisclosure;

FIG. 42 illustrates an example of distinguishing resources forcommunication between one UE pair from resources for communicationbetween another UE pair according to an embodiment of the presentdisclosure;

FIG. 43 illustrates an operation for allocating and exchanging a unifiedC-RNTI according to an embodiment of the present disclosure;

FIG. 44 illustrates an example of distinguishing resources for UE paircommunication from other resources within the coverage area of an eNBaccording to an embodiment of the present disclosure;

FIG. 45 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for communication betweenan eNB and a UE of the UE pair according to an embodiment of the presentdisclosure;

FIG. 46 illustrates an example of distinguishing resources for UE paircommunication from resources for other UE pair communication accordingto an embodiment of the present disclosure;

FIG. 47 illustrates an example of distinguishing resources for UE paircommunication from other resources within the coverage area of an eNBaccording to an embodiment of the present disclosure;

FIG. 48 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for communication betweenan eNB and a UE of the UE pair according to an embodiment of the presentdisclosure;

FIG. 49 illustrates an example of distinguishing resources forcommunication between one UE pair from resources for communicationbetween another UE pair according to an embodiment of the presentdisclosure;

FIG. 50 is a block diagram of an eNB according to an embodiment of thepresent disclosure; and

FIG. 51 is a block diagram of a UE according to an embodiment of thepresent disclosure.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components, and structures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skilled in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

A Base Station (BS) is an entity that communicates with a User Equipment(UE). The term BS may be replaced with Node B, evolved Node B (eNB oreNode B), Access Point (AP), and the like.

A UE is an entity that communicates with a BS. The term UE may bereplaced with Mobile Station (MS), Mobile Equipment (ME), device,terminal, and the like.

FIG. 1 illustrates a Device-to-Device (D2D) communication environmentaccording to the related art.

Referring to FIG. 1, a pair of a first UE (UE1) and a second UE (UE2)are connected to an eNB and also to each other for direct communication.UE1 and UE2 communicate with the eNB using a DownLink (DL) frequency F1and an UpLink (UL) frequency F2 in a FDD (Frequency Division Duplex)system. The UL frequency F2 is also used for D2D communication betweenUE1 and UE2. Resources of the UL frequency F2 are controlled by the eNB.In a TDD (Time Division Duplexed) system, UE1 and UE2 communicate withthe eNB using a frequency F1 comprising of UL and DL time slots whereinUL time slots are used by UE 1 and UE 2 to transmit to eNB and DL timeslots are used by UE1 and UE2 to receive from eNB. The UL time slots arealso used for D2D communication between UE1 and UE2. It is to be notedthat UE may also communicate with multiple UEs concurrently.

FIG. 2 illustrates a case in which a plurality of UE pairs connected toan eNB participates in D2D communication according to an embodiment ofthe present disclosure.

Referring to FIG. 2, all of UE1, UE2, a third UE (UE3), a fourth UE(UE4), and a fifth UE (UE5) communicate with the eNB using the DLfrequency D1 and the UL frequency F2 in a FDD (Frequency DivisionDuplex) system. As described before, UE pairs, herein, a UE1-UE2 pairand a UE4-UE5 pair perform D2D communication using the UL frequency F2.In a TDD (Time Division Duplexed) system, UE(s) communicate with the eNBusing a frequency F1 comprising of UL and DL time slots wherein UL timeslots is used by UE(s) to transmit to eNB and DL time slots are used byUE(s) to receive from eNB. The UL time slots are also used for D2Dcommunication between UE1-UE2 and UE4-UE5.

In this case, there is a need for a method for signaling Transmission(Tx) resources and/or Reception (Rx) resources for the UEs involved inD2D communication, a method for identifying a Tx role and an Rx rolebetween the UEs during D2D communication, a method for distinguishing Txresources from Rx resources for each UE. Embodiments of the presentdisclosure provide these methods.

Embodiment 1

A method for allocating resources for D2D transmission in one embodimentis described below.

A UE within the coverage area of a network may participate in D2Dcommunication and may also communicate with an eNB. The UE requestsresources for D2D communication to an eNB of a serving cell within thenetwork coverage area. In order to allocate the resources, the eNBdetermines whether the UE has requested the resources for D2Dcommunication or for UL transmission to the eNB. The resources for D2Dcommunication and the resources for UL transmission to the eNB areallocated to the UE through a DL control channel, Physical DownlinkControl Channel (PDCCH) or Enhanced PDCCH (EPDCCH). When the UE receivesand decodes the DL control channel (the PDCCH or the EPDCCH) masked withits IDentifier (ID), then the UE determines whether the allocatedresources are for D2D communication or for UL transmission to the eNB.

Hereinbelow, three methods for allocating resources for D2D transmissionaccording to embodiments of the present disclosure will be described.

FIG. 3 illustrates a method for allocating resources for D2Dtransmission according to an embodiment of the present disclosure.

Resources for UL transmission to the eNB and resources for D2Dcommunication are indicated through a control channel transmitted by theeNB in different DL subframes. A UE is aware of a DL subframe indicatingresources for UL transmission to the eNB and a DL subframe indicatingresources for D2D communication. Alternately, resources for ULtransmission to the eNB and resources for D2D communication may beindicated through a control channel transmitted by the eNB in the sameDL subframe. The UE determines that resources are for D2D communicationif the resources indicated in the control channel belong to a set ofresources reserved in a UL subframe corresponding to a DL subframe inwhich the control channel is received. The UE uses a single Cell RadioNetwork Temporary Identity (C-RNTI) to determine the resources for eachtype of communication.

Referring to FIG. 3, the UE is in a connected state and assigned aC-RNTI by the eNB. If the UE wants to transmit control and/or datapackets through a D2D communication link, the UE transmits a D2D BufferStatus Report (BSR) to the eNB in operation 301. The D2D BSR isdifferent from a general BSR wherein the UE sends the general BSR to eNBto request resources for UL transmission to eNB. A Logical Channel ID(LCID) identifies the D2D BSR from a general BSR. ALCID is newlyreserved to indicate the D2D BSR. The LCID may be included in the D2DBSR. Alternatively, the LCID may be included in a Medium Access Control(MAC) subheader indicating a MAC control element having the D2D BSR in aMAC Packet Data Unit (PDU). The D2D BSR may also include a destinationID. The destination ID is the ID of a destination to which the UE wantsto transmit control and/or data packets through the D2D communicationlink. The destination ID may be a unicast address of another UE, groupcast address of a group of UEs, or broadcast address. The D2D BSR mayalso include buffer size and logical channel group ID. Multiple logicalchannels are typically grouped together and buffer status of group ofthese logical channels is sent using one buffer status report.

If Physical Uplink Control Channel (PUCCH) resources are available fortransmission of the D2D BSR, the resources for the D2D BSR may beobtained using a general method such as transmitting a schedulingrequest to the eNB. Alternately the resources for the D2D BSR may beobtained by transmitting a random access preamble to the eNB on a RandomAccess CHannel (RACH). D2D BSR may also be sent in resources alreadyallocated by eNB for UL transmission to eNB.

Upon receipt of the BSR, the eNB in operation 303 determines whether theBSR is for D2D communication or for UL transmission to eNB. Thisdetermination is done using the LCID. If the BSR is a D2D BSR then ENBallocates resources for D2D transmission in operation 305 and transmitsa grant for D2D transmission on a PDCCH or EPDCCH in a DL subframecorresponding to a UL subframe reserved for D2D communication inoperation 307. A Control Information format carrying D2D resourceinformation is the same as or different from a control informationformat carrying resource information for transmission of a UE to an eNBor for reception from an eNB. The Cyclic Redundancy Check (CRC) of PDCCHor EPDCCH carrying control information is masked with the C-RNTI.

If the UE transmits a Scheduling Assignment (SA) for the D2Dcommunication link in addition to a data packet, upon receipt of the D2DBSR, the eNB may allocate resources for transmission of both the SA andthe data packet and indicate the allocated resources using the same ordifferent PDCCHs or EPDCCHs. Alternatively or additionally, upon receiptof the D2D BSR, the eNB may allocate resources for transmitting the SAonly. The resources for the data packet may be fixed relative to thelocation of the SA and/or resources for the SA.

In an alternate embodiment of method illustrated in FIG. 3, instead ofBSR, a D2D scheduling request can be transmitted on PUCCH wherein thePUCCH resources are reserved and/or assigned to UE for D2D SRtransmission. eNB determines that UE needs resources for D2Dcommunication on receiving the D2D scheduling request in the PUCCHresources reserved and/or assigned to UE for D2D SR transmission.

FIG. 4 illustrates another method for allocating resources for D2Dtransmission according to an embodiment of the present disclosure.

Control information format delivered on a control channel indicatingresources for communication with an eNB and control information formatdelivered on a control channel indicating resources for D2Dcommunication may have different formats. The control information formatof the control channel indicating resources for D2D communication may bedesigned such that the size of the control information format isdifferent from the size of general control information format, so thatwhen a UE receives and decodes the control channel, the UE may determinewhether the control information indicates resources for D2Dcommunication or not.

Referring to FIG. 4, a UE is in a connected state and assigned a C-RNTIby an eNB. If the UE wants to transmit control and/or data packetsthrough a D2D communication link, the UE transmits a D2D BSR to the eNBin operation 401. The D2D BSR is different from a general BSR whereinthe UE sends the general BSR to eNB to request resources for ULtransmission to eNB. The D2D BSR is distinguished from a general BSR byan LCID. The LCID is reserved to indicate the D2D BSR. The LCID may beincluded in the D2D BSR. Alternatively or additionally, the LCID may beincluded in a MAC subheader indicating a MAC control element with theD2D BSR in a MAC PDU. The D2D BSR may also include a destination ID. Thedestination ID is the ID of a destination to which the UE wants totransmit control and/or data packets through the D2D communication link.The destination ID may be a unicast address of another UE, group castaddress of a group of UEs, or broadcast address. The D2D BSR may alsoinclude buffer size and logical channel group ID. Multiple logicalchannels are typically grouped together and buffer status of group ofthese logical channels is sent using one buffer status report.

If PUCCH resources are available for transmission of the D2D BSR, theresources for the D2D BSR may be obtained using a general method such astransmitting a scheduling request to the eNB. Alternately the resourcesfor the D2D BSR may be obtained by transmitting a random access preambleto the eNB on an RACH.). D2D BSR may also be sent in resources alreadyallocated by eNB for UL transmission to eNB.

Upon receipt of the BSR, the eNB in operation 403 determines whether theBSR is for D2D communication or for UL transmission to eNB. Thisdetermination is done using the LCID. If the BSR is a D2D BSR the eNBallocates resources for D2D transmission in operation 405 and transmitsa grant for D2D transmission on a PDCCH or EPDCCH in operation 407. Acontrol information format carrying D2D resource information isdifferent from a control information format carrying resourceinformation for transmission of a UE to an eNB or for reception from aneNB. The CRC of PDCCH or EPDCCH carrying control information is maskedwith the C-RNTI.

If the UE transmits an SA for the D2D communication link in addition toa data packet, upon receipt of the D2D BSR, the eNB may allocateresources for transmission of both the SA and the data packet and mayindicate the allocated resources using the same PDCCH or EPDCCH ordifferent PDCCHs or EPDCCHs. Alternatively or additionally, upon receiptof the D2D BSR, the eNB may allocate resources for transmission of theSA only. The resources for the data packet may be fixed relative to thelocation of the SA and/or resources for the SA.

In an alternate embodiment of method illustrated in FIG. 4, instead ofBSR, a D2D scheduling request can be transmitted on PUCCH wherein thePUCCH resources are reserved and/or assigned for D2D SR transmission.eNB determines that UE needs resources for D2D communication onreceiving the D2D scheduling request in the PUCCH resources reservedand/or assigned to UE for D2D SR transmission.

FIG. 5 illustrates a third method for allocating resources for D2Dtransmission according to an embodiment of the present disclosure.

Different C-RNTIs may be assigned to a UE for communication with an eNBand D2D communication. Therefore, the eNB uses the one or more C-RNTIsassigned for D2D communication on a control channel carrying resourcesfor D2D communication and the one or more C-RNTIs assigned forcommunication between the UE and the eNB on a control channel carryingresources for communication between the UE and the eNB.

Referring to FIG. 5, a UE is in a connected state and assigned one ormore C-RNTIs by an eNB for communication with eNB. If the UE wants totransmit a signal through a D2D communication link, the UE transmits aD2D communication request message (or a D2D communication interestindication message or UE assistance information message with D2Dcommunication interest indication wherein the interest indication mayindicate that UE is interested in D2D communication or it may indicatethat UE is interested in transmission for D2D communication or it mayindicate that UE is interested in reception for D2D communication or itmay indicate that UE is interested in both transmission and receptionfor D2D communication) to the eNB in operation 501. The eNB assigns aD2D Radio Network Temporary Identifier (RNTI) (D2D-RNTI) to the UE inresponse to the D2D communication request message (or D2D communicationinterest indication message or UE assistance information message withD2D communication interest indication) in operation 503. In oneembodiment the D2D communication response message in operation 503 maybe a RRC connection reconfiguration message. If the UE wants to transmitcontrol and/or data packets through a D2D communication link, the UEtransmits a D2D BSR to the eNB in operation 505. The D2D BSR isdifferent from a general BSR transmitted to the eNB for requesting agrant for communication between the UE and the eNB to the eNB. An LCIDdistinguishes the D2D BSR from the general BSR. The LCID is reserved toindicate the D2D BSR. The LCID may be included in the D2D BSR.Alternatively or additionally, the LCID may be included in a MACsubheader which indicates a MAC control element having the D2D BSR in aMAC PDU. The D2D BSR may also include a destination ID. The destinationID is the ID of a destination to which the UE wants to transmit controland/or data packets through the D2D communication link. The destinationID may be a unicast address of another UE, group cast address of a groupof UEs, or broadcast address. The D2D BSR may also include buffer sizeand logical channel group ID. Multiple logical channels are typicallygrouped together and buffer status of group of these logical channels issent using one buffer status report.

If PUCCH resources are available for transmission of the D2D BSR, theresources for the D2D BSR may be obtained using a general method such astransmitting a scheduling request to the eNB. Alternately the resourcesfor the D2D BSR may be obtained by transmitting a random access preambleto the eNB on an RACH. D2D BSR may also be sent in resources alreadyallocated by eNB for UL transmission to eNB.

Upon receipt of the BSR, the eNB in operation 507 determines whether theBSR is for D2D communication or for UL transmission to eNB. Thisdetermination is done using the LCID. If the BSR is a D2D BSR the eNBallocates resources for D2D transmission in operation 509 and transmitsa grant for D2D transmission on a PDCCH or EPDCCH in operation 511. Acontrol information format carrying D2D resource information may be sameor different from a control information format carrying resourceinformation for transmission of a UE to an eNB. The CRC of PDCCH orEPDCCH carrying control information is masked with the D2D-RNTI.

If the UE transmits an SA for the D2D communication link in addition toa data packet, upon receipt of the D2D BSR, the eNB may allocateresources for transmission of both the SA and the data packet and mayindicate the allocated resources using the same PDCCH or EPDCCH ordifferent PDCCHs or EPDCCHs. Alternatively or additionally, upon receiptof the D2D BSR, the eNB may allocate resources for transmission of theSA only. The resources for the data packet may be fixed relative to thelocation of the SA and/or resources of the SA.

In an alternate embodiment of method illustrated in FIG. 5, instead ofBSR, a D2D scheduling request can be transmitted on PUCCH wherein thePUCCH resources are reserved and/or assigned for D2D SR transmission.eNB determines that UE needs resources for D2D communication onreceiving the D2D scheduling request in the PUCCH resources reservedand/or assigned to UE for D2D SR transmission.

In an alternate embodiment of method illustrated in FIG. 5, the D2Dcommunication request in operation 501 may be indicated duringconnection setup. The D2D-RNTI may be assigned in addition to the C-RNTIduring the connection setup. Alternately the UE does not indicateinterest in D2D communication to eNB during connection setup. The eNBautonomously assigns the D2D-RNTI in addition to the C-RNTI during theconnection setup if the UE is authorized to perform D2D communication.eNB determines that UE is authorized to perform D2D communication basedon UE context received from MME during the connection setup procedure.Alternatively or additionally, the eNB may allocate the D2D-RNTI afterreceiving the D2D BSR.

A method for allocating resources for D2D reception in one embodiment isdescribed below.

According to an embodiment of the present disclosure, a resource poolincluding Rx resources may be indicated to a D2D UE interested in D2Dcommunication. The resource pool may be preconfigured in the D2D UE. TheD2D UE may acquire the resource pool from a D2D server in the network.The eNB may broadcast the resource pool using system information. Theresource pool may be signaled to the D2D UE by dedicated signaling. Theresource pool for reception may include resources of a neighbor cell aswell resources of a serving cell.

If the UE transmits an SA for the D2D communication link in addition toa data packet, the resource pool for reception includes resources for SAreception. The resources for the data packet are determined bymonitoring the SA by the receiving UE. Alternatively or additionally,both an SA resource pool and a data resource pool may be indicated tothe D2D UE.

Embodiment 2

In an embodiment of the present disclosure, control channel istransmitted to both transmitting UE and receiving UE to indicateresources for transmission and reception on D2D communication link. Inthis embodiment the transmitting UE and receiving UE may be connected tosame eNB or different eNB. An eNB enables a UE to distinguish Txresources from Rx resources using a Tx/Rx indicator along with resourceinformation.

Different eNBs communicating with UEs coordinate with each other todetermine resources for D2D communication between the UEs and signal thedetermined resources to the UEs. For example, if UE1 belonging to afirst eNB (eNB1) communicates with UE2 belonging to a second eNB (eNB2)by D2D communication, eNB1 signals resources determined for the D2Dcommunication between UE1 and UE2 to UE1 and eNB2 signals the resourcesdetermined for the D2D communication between UE1 and UE2 to UE2. Theresources are determined for transmission of packets through a D2Dcommunication link. The resources may also be allocated semi-staticallysuch that the allocated resources are valid during a plurality ofTransmission Time Intervals (TTIs). The resources may also be allocatedstatically such that the determined resources are valid for the durationof a connection between UE1 and UE2.

A method for signaling allocated resources is performed as follows.

An eNB transmits resources for D2D communication between a UE pair in aDL subframe and a control region in the DL subframe indicates theresources for D2D communication as well as resources for communicationwith the eNB. The resources for D2D communication are indicated to theUEs of the UE pair by their respective eNBs. That is, the eNB associatedwith each UE of the UE Pair transmits control channel carrying resourceallocation information to the UE. A CRC of the control channel may bemasked with a UE ID (example C-RNTI or D2D-RNTI) of the UE.

For example, if UE1 and UE2 belong to different eNBs, UE1 uses allocatedresources for transmission, and UE2 uses the allocated resources forreception, eNB1 transmits a first PDCCH/EPDCCH (PDCCH1 or EPDCCH1) toUE1 and eNB2 transmits a second PDCCH/EPDCCH (PDCCH2 or EPDCCH2) to UE2in order to indicate resources in which UE1 transmits data and UE2receives data. The CRC of PDCCH1/EPDCCH1 transmitted by eNB1 is maskedwith a UE ID of UE1, and the CRC of PDCCH2/EPDCCH2 transmitted by eNB2is masked with a UE ID of UE2. Both the PDCCHs/EPDCCHs may betransmitted in the same DL subframe or different DL subframes.

In another example, if UE1 and UE2 belong to same eNB1, UE1 usesallocated resources for transmission, and UE2 uses the allocatedresources for reception, eNB1 transmits PDCCH1/EPDCCH1 to UE1 andPDCCH2/EPDCCH2 to UE2 in order to indicate the resources in which UE1transmits and UE2 receives. The CRC of PDCCH1/EPDCCH1 is masked with theUE ID of UE1 and the CRC of PDCCH2/EPDCCH2 is masked with the UE ID ofUE2. Both the PDCCHs/EPDCCHs may be transmitted in the same DL subframeor different DL subframes.

Resources for communication with eNB and resources for D2D communicationindicated on control channel are distinguished by UE/eNB using themethods illustrated in FIG. 3, 4 and FIG. 5.

A method for identifying Tx resources from Rx resources by a UE will bedescribed below.

Upon receipt of information about resources allocated for D2Dcommunication, the UE needs to determine whether the allocated resourcesare for transmission or reception. An eNB adds a 1-bit Tx/Rx indicatorin a control channel carrying the resource allocation information. Ifthe Tx/Rx indicator is 1, this may mean Tx resources and if the Tx/Rxindicator is 0, this may mean Rx resources. Upon receipt of a controlchannel carrying resource allocation information with a UE ID of the UE(for example, a C-RNTI of the UE), if a Tx/Rx indicator is set to 0 inthe received information, the UE receives data in resources indicated bythe resource allocation information. If the Tx/Rx indicator is set to 1in the received information, the UE transmits data in the indicatedresources. The Tx/Rx indicator may be included as an information fieldin the control channel or may be included in a CRC mask used to generatea CRC for the control channel.

Now, a description will be given of a method for identifying atransmitting UE and a receiving UE using a Tx/Rx indicator and Tx and Rxindexes in the respective cases where a UE is allocated Rx resources andTx resources.

First, a method for identifying a transmitting UE in the case where Rxresources are allocated to a UE will be described below.

Each UE may be connected to a plurality of UEs. In the case where Rxresources are allocated to the UE, the UE needs to determine from whichUE it has to receive data using the allocated resources. To identify thetransmitting UE, the UE may use an Rx index. For example, if UE1 isconnected to UE2 and a third (UE3) for D2D communication and Rxresources are allocated to UE1, UE1 may receive data from UE2 and UE3.For a connection between UE1 and UE2, Rx index 0 may be assigned to UE1,and for a connection between UE1 and UE3, Rx index 1 may be assigned toUE1. If UE1 receives a control channel with its UE ID and a Tx/Rxindicator set to 0, UE1 receives data in resources indicated by thecontrol channel. UE1 may identify a transmitting UE using an Rx indexset in the control channel. The Rx index may be included as aninformation field in the control channel or may be included in a CRCmask. Additionally, the Rx index may be unique across a plurality ofpairs of the UE and other UEs, and an Rx index assigned to each UE maybe maintained for the UE independently.

Each UE may be connected to a plurality of UEs. In the case where Txresources are allocated to the UE, the UE needs to determine to which UEit has to transmit data using the allocated resources. For this purpose,a Tx index (Tx_Idx) may be used. For example, if UE1 is connected to UE2and UE3 and Tx resources are allocated to UE1, UE1 may transmit data toUE2 and UE3. For a connection between UE1 and UE2, Tx_Idx 0 may beassigned to UE1, and for a connection between UE1 and UE3, Tx_Idx 1 maybe assigned to UE1. If UE1 receives a control channel with its UE ID anda Tx/Rx indicator set to 1, UE1 transmits data in resources indicated bythe control channel. UE1 may identify a receiving UE by a Tx index setin the control channel. The Tx index may be included as an informationfield in the control channel or may be included in a CRC mask. The Txindex may be unique across a plurality of pairs of the UE and other UEs,and a Tx index assigned to each UE may be maintained for the UEindependently.

FIGS. 6 and 7 illustrate a method for allocating resources for D2Dcommunication between cells according to an embodiment of the presentdisclosure. UE A operates as a transmitting UE and UE B operates as areceiving UE in FIG. 6, whereas UE A operates as a receiving UE and UE Boperates as a transmitting UE in FIG. 7.

Referring to FIG. 6, during D2D connection setup, eNB 1 assigns Tx_Idx pand Rx_Idx r to UE A, for communication with UE B in operation 601.During the D2D connection setup, eNB2 assigns Tx_Idx s and Rx_Idx q toUE B, for communication with UE A in operation 601. In operation 603,eNB1 and eNB2 determine resources for D2D communication between UE A andUE B by coordinating with each other. If eNB 1 and eNB2 determine to useresources X for data transmission from UE A to UE B, eNB1 transmits toUE A PDCCH1 having a CRC masked with a UE ID (for example C-RNTI) of UEA in operation 605. PDCCH1 delivers information about resources X forthe D2D communication. UE A receives and decodes PDCCH1 using its UE ID.UE A then determines that it has to use the resources indicated byPDCCH1, for transmission of data to UE B, based on a Tx/Rx indicator anda Tx index. If the Tx/Rx indicator is set to 1, it indicates to UE Athat resources X are allocated to UE A, for transmission in operation607. If the Tx index is set to p, this indicates that UE A shouldtransmit data to UE B corresponding to Tx index p in operation 609.Likewise, eNB2 transmits to UEB PDCCH2 having a CRC masked with a C-RNTIof UE B in operation 611. PDCCH2 delivers information about resources Xfor the D2D communication. UE B receives and decodes PDCCH2 using itsC-RNTI. UE B determines that it has to use the resources indicated byPDCCH2, for reception of data from UE A, based on a Tx/Rx indicator andan Rx index. If the Tx/Rx indicator is set to 0, it indicates to UE Bthat resources X are allocated to UE B, for reception in operation 613.If the Rx index is set to q, this indicates that UE B should receivedata from UE A corresponding to Rx index q in operation 615. UE Atransmits a packet to UE B in resources X in operation 617.

Referring to FIG. 7, during D2D connection setup, eNB1 assigns Tx_Idx pand Rx_Idx r to UE A, for communication with UE B in operation 701.During the D2D connection setup, eNB2 assigns Tx_Idx s and Rx_Idx q toUE B, for communication with UE A in operation 701. In operation 703,eNB1 and eNB2 determine resources for D2D communication between UE A andUE B by coordinating with each other. If eNB1 and eNB2 determine to useresources Y for data transmission from UE B to UE A, eNB1 transmits toUE A PDCCH3 having a CRC masked with the C-RNTI of UE A in operation705. PDCCH3 delivers information about resources Y for the D2Dcommunication. UE A receives and decodes PDCCH3 using its C-RNTI. UE Adetermines that it has to use the resources indicated by PDCCH3, forreception of data from UE B, based on a Tx/Rx indicator and an Rx index.If the Tx/Rx indicator is set to 0, it indicates to UE A that resourcesY are allocated to UE A, for reception in operation 707. If the Rx indexis set to r, this indicates that UE A should receive data from UE Bcorresponding to Rx index r in operation 709. Likewise, eNB2 transmitsto UE B PDCCH4 having a CRC masked with the UE ID (for example C-RNTI)of UE B in operation 711. PDCCH4 delivers information about resources Yfor the D2D communication. UE B receives and decodes PDCCH4 using its UEID. UE B determines that it has to use the resources indicated byPDCCH4, for transmission of data to UE A, based on a Tx/Rx indicator anda Tx index. If the Tx/Rx indicator is set to 1, it indicates to UE Bthat resources Y are allocated to UE B, for transmission in operation713. If the Tx index is set to s, this indicates that UE B shouldtransmit data to UE A corresponding to Tx index s in operation 715. UE Btransmits a packet to UE A in resources Yin operation 717.

FIGS. 8 and 9 illustrate a method for allocating resources for D2Dcommunication within a cell according to an embodiment of the presentdisclosure. UE A operates as a transmitting UE and UE B operates as areceiving UE in FIG. 8, whereas UE A operates as a receiving UE and UE Boperates as a transmitting UE in FIG. 9.

Referring to FIG. 8, both UE A and UE B communicate with the same eNB.During D2D connection setup, eNB1 assigns Tx_Idx p and Rx_Idx r to UE A,for communication with UE B and assigns Tx_Idx s and Rx_Idx q to UE B,for communication with UE A in operation 801. eNB1 determines resourcesfor D2D communication between UE A and UE B. If eNB1 determines to useresources X for data transmission from UE A to UE B, eNB1 transmitsPDCCH1 having a CRC masked with the UE ID (for example C-RNTI) of UE Ato UE A in operation 803. PDCCH1 delivers information about resources Xfor the D2D communication. UE A receives and decodes PDCCH1 using its UEID. UE A determines that it has to use the resources indicated byPDCCH1, for transmission of data to UE B, based on a Tx/Rx indicator anda Tx index. If the Tx/Rx indicator is set to 1, it indicates to UE Athat resources X are allocated to UE A, for transmission in operation805. If the Tx index is set to p, this indicates that UE A shouldtransmit data to UE B corresponding to Tx index p in operation 807. eNB1also transmits PDCCH2 having a CRC masked with the UE ID of UE B to UE Bin operation 809. PDCCH2 delivers information about resources X for theD2D communication. UE B receives and decodes PDCCH2 using its UE ID. UEB determines that it has to use the resources indicated by PDCCH2, forreception of data from UE A, based on a Tx/Rx indicator and an Rx index.If the Tx/Rx indicator is set to 0, it indicates to UE B that resourcesX are allocated to UE B, for reception in operation 811. If the Rx indexis set to q, this indicates that UE B should receive data from UE Acorresponding to Rx index q in operation 813. UE A transmits a packet toUE B in resources X in operation 815. In FIG. 8, the order of operations803 to 807 and operations 809 to 813 may be changed.

Referring to FIG. 9, during D2D connection setup, eNB1 assigns Tx_Idx pand Rx_Idx=r to UE A, for communication with UE B and assigns Tx_Idx sand Rx_Idx q to UE B, for communication with UE A in operation 901. eNB1determines resources for D2D communication between UE A and UE B. IfeNB1 determines to use resources Y for data transmission from UE B to UEA, eNB1 transmits to UE B PDCCH3 having a CRC masked with the UE ID ofUE B in operation 903. PDCCH3 delivers information about resources Y forthe D2D communication. UE B receives and decodes PDCCH3 using its UE ID.UE B determines that it has to use the resources indicated by PDCCH3,for transmission of data to UE A, based on a Tx/Rx indicator and a Txindex. If the Tx/Rx indicator is set to 1, it indicates to UE B thatresources Y are allocated to UE B, for transmission in operation 905. Ifthe Tx index is set to s, this indicates that UE B should transmit datato UE A corresponding to Tx index s in operation 907. Likewise, eNB1transmits to UE A PDCCH4 having a CRC masked with the UE ID of UE A inoperation 909. PDCCH4 delivers information about resources Y for the D2Dcommunication. UE A receives and decodes PDCCH4 using its UE ID. UE Adetermines that it has to use the resources indicated by PDCCH4, forreception of data from UE B, based on a Tx/Rx indicator and an Rx index.If the Tx/Rx indicator is set to 0, it indicates to UE A that resourcesY are allocated to UE A, for reception in operation 911. If the Rx indexis set to r, this indicates that UE A should receive data from UE Bcorresponding to Rx index r in operation 913. UE B transmits a packet toUE A in resources Y in operation 915. In FIG. 9, the order of operations903 to 907 and operations 909 to 913 may be changed.

FIG. 10 illustrates a method for allocating a Tx index and an Rx indexin allocating resources for D2D communication between cells according toan embodiment of the present disclosure.

Referring to FIG. 10, UE A has discovered UE B. When UE A wants toestablish a D2D connection with UE B, UE A triggers direct connectionsetup and UE A transmits a direct communication request message to eNB1in operation 1001. The direct communication request includes a UE ID ofUE A and a UE ID of UE B. According to an embodiment, the UE ID of eachUE may be an ID assigned to the UE for Proximity Service (ProSe)communication (that is, a ProSe UE ID). Or the UE ID may be an idle modeID assigned to the UE (that is, an SAE Temporary Mobile SubscriberIdentity (S-TMSI)). Or the UE ID may be a Globally Unique TemporaryIdentifier (GUTI) assigned to the UE. UE A may discover the UE ID of UEB during the discovery of UE B.

Upon receipt of the direct communication request message from UE A, eNB1verifies the direct communication request message and transmits a directcommunication request message including the UE ID of UE B to a MobilityManagement Entity (MME) in operation 1003. The MME determines a cell oreNB of UE B in operation 1005. In the case where eNB1 and the eNB of UEB are under the same MME, if UE B is in idle mode, the MME pages UE B sothat UE B may transition to connected mode. In the case where eNB1 andthe eNB of the UE B are under different MMEs, the MME contacts the MMEof UE B in order to determine the cell of UE B. When determining thecell of UE B, the MME transmits a direct communication response messageto eNB1 in operation 1007. The direct communication response messageincludes information about the cell or eNB of UE B. eNB1 assigns a Txindex and an Rx index to UE A and transmits the assigned Tx and Rxindexes of UE A and the C-RNTI of UE A in a direct communicationresponse message to UE A in operation 1009. Only if the C-RNTI is newlyassigned to UE A, eNB1 may include the C-RNTI of UE A. If a C-RNTI hasnot been assigned to UE A yet, eNB1 may assign the C-RNTI to UE A.Further, eNB1 may transmit other parameters related to directcommunication in the direct communication response message to UE A. Uponreceipt of the direct communication response message, UE A transmits adirect communication complete message to eNB1 in operation 1011.

Upon receipt of the direct communication request message from eNB1 oranother MME, the MME transmits a direct communication request message toeNB2 of UE B indicated by the received direct communication requestmessage in operation 1013. It is assumed in FIG. 10 that UE A and UE Bare under the same MME. The direct communication request messageincludes the UE ID of UE A, the UE ID of UE B, and information about thecell or eNB of UE A. Upon receipt of the direct communication requestmessage, eNB2 assigns a Tx index and an Rx index to UE B and transmitsthe assigned Tx and Rx indexes of UE B and the C-RNTI of UE B in adirect communication response message to UE B in operation 1015. eNB2may include the C-RNTI of UE B only if the C-RNTI is newly assigned toUE B. If a C-RNTI has not been assigned to UE B yet, eNB2 assigns theC-RNTI to UE B. Further, eNB2 may transmit other parameters related todirect communication in the direct communication response message. Uponreceipt of the direct communication response message, UE B transmits adirect communication complete message to eNB2 in operation 1017. eNB1and eNB2 determine resources for D2D communication in operation 1019 insubstantially the same manner as in operation 603 of FIG. 6 andoperation 703 of FIG. 7.

A UE may maintain its Tx index and Rx index. That is, the UE may assigna Tx index and an Rx index for its connection to another UE and transmitinformation about the assigned Tx and Rx indexes to an eNB during directconnection setup. The eNB stores the information and uses it fortransmitting a PDCCH to the UE. The Tx and Rx indexes maintained by theUE may be transmitted to the eNB in a direct communication requestmessage or a direct communication complete message. The property of a Txindex and an Rx index is the same irrespective of whether they areassigned by the eNB or the UE. If the eNB allocates a Tx index and an Rxindex, the eNB should maintain information about the Tx index and the Rxindex. If the UE allocates a Tx index and an Rx index, the UE shouldmaintain information about the Tx index and the Rx index, therebyreducing the load of the eNB.

FIG. 11 illustrates another method for allocating a Tx index and an Rxindex in allocating resources for D2D communication between cellsaccording to an embodiment of the present disclosure.

Referring to FIG. 11, UE A initiates direct communication setup with UEB and transmits a direct communication request message including its UEID to UE B in operation 1101. According to an embodiment, the UE ID maybe an ID assigned to UE A for ProSe communication (that is, a ProSe UEID). Or the UE ID may be an idle mode ID assigned to UE A (that is, anS-TMSI). Or the UE ID may be a GUTI assigned to UE A. If UE B acceptsthe direct communication request from UE A, UE B transmits a directcommunication response message including its UE ID to UE A in operation1103. UE A and UE B transmit direct communication request messages toeNB1 and eNB2 respectively in operations 1105 and 1107. UE A and UE Binclude their UE IDs in the direct communication request messages. Theorder of operations 1105 and 1107 may be changed.

Upon receipt of the direct communication request message from UE A, eNB1verifies the direct connection request message, assigns a Tx index andan Rx index to UE A, and transmits the assigned Tx index and Rx indexand the C-RNTI of UE A in a direct communication response message to UEA in operation 1109. Only if the C-RNTI is newly assigned to UE A, theC-RNTI of UE A may be included. If a C-RNTI has not been assigned to UEA yet, eNB1 assigns a C-RNTI to UE A. eNB1 may transmit other parametersrelated to direct communication in the direct communication responsemessage to UE A. Upon receipt of the direct communication responsemessage from eNB1, UE A transmits a direct communication completemessage to eNB1 in operation 1113.

Likewise, upon receipt of the direct communication request message fromUE B, eNB2 verifies the direct connection request message, assigns a Txindex and an Rx index to UE B, and transmits the assigned Tx index andRx index and the C-RNTI of UE B in a direct communication responsemessage to UE B in operation 1111. Only if the C-RNTI is newly assignedto UE B, the C-RNTI of UE B may be included. If a C-RNTI has not beenassigned to UE B yet, eNB2 assigns the C-RNTI to UE B. eNB2 may transmitother parameters related to direct communication in the directcommunication response message to UE B. Upon receipt of the directcommunication response message from eNB2, UE B transmits a directcommunication complete message to eNB2 in operation 1115. UE A and UE Boperate for D2D communication.

Upon receipt of the direct communication request message from UE A, eNB1determines the cell or eNB of UE B through the MME, as described withreference to FIG. 10. Upon receipt of the direct communication requestmessage from UE B, eNB2 performs the same operation. eNB1 and eNB2determine resources for D2D communication in operation 1019 as inoperation 603 of FIG. 6 and operation 703 of FIG. 7.

A UE may maintain a Tx index and an Rx index. That is, the UE may assigna Tx index and an Rx index for its connection with another UE andtransmit information about the assigned Tx index and Rx index to an eNBduring direct connection setup. The eNB stores the information and usesit for transmitting a PDCCH to the UE. The Tx index and Rx index managedby the UE may be transmitted in a direct communication request messageor a direct communication complete message to the eNB. The property of aTx index and an Rx index is the same irrespective of whether they areassigned by the eNB or the UE. If the eNB assigns a Tx index and an Rxindex, the eNB should maintain the Tx index and the Rx index. If the UEassigns a Tx index and an Rx index, the UE should maintain the Tx indexand the Rx index, thereby reducing the load of the eNB.

FIG. 12 illustrates a method for allocating a Tx index and an Rx indexin allocating resources for D2D communication within a cell according toan embodiment of the present disclosure.

Referring to FIG. 12, UE A has discovered UE B. When UE A wants toestablish a D2D connection with UE B, UE A triggers direct connectionsetup and transmits a direct communication request message to eNB1 inoperation 1201. The direct communication request message includes the UEID of UE A and the UE ID of UE B. According to an embodiment, the UE IDof each UE may be an ID assigned to the UE for ProSe communication (thatis, a ProSe UE ID). Or the UE ID may be an idle mode ID assigned to theUE (that is, an S-TMSI). Or the UE ID may be a GUTI assigned to the UE.UE A may discover the UE ID of UE B during the discovery of UE B.

Upon receipt of the direct communication request message from UE A, eNB1verifies the direct communication request message and transmits a directcommunication request message including the UE ID of UE B to the MME inoperation 1203. The MME determines the cell or eNB of UE B in operation1205. In the case where eNB1 and the eNB of UE B are under the same MME,if UE B is in idle mode, the MME pages UE B so that UE B may transitionto connected mode. In the case where eNB1 and the eNB of the UE B areunder different MMEs, the MME contacts the MME of UE B in order todetermine the cell of UE B. When determining the cell of UE B, the MMEtransmits a direct communication response message to eNB1 in operation1207. The direct communication response message includes informationabout the cell or eNB of UE B. eNB1 assigns a Tx index and an Rx indexto UE A and transmits the assigned Tx index and Rx index of UE A and theC-RNTI of UE A in a direct communication response message to UE A inoperation 1209. Only if the C-RNTI is newly assigned to UE A, eNB1 mayinclude the C-RNTI of UE A. If a C-RNTI has not been assigned to UE Ayet, eNB1 may assign the C-RNTI to UE A. Further, eNB1 may transmitother parameters related to direct communication in the directcommunication response message to UE A. Upon receipt of the directcommunication response message, UE A transmits a direct communicationcomplete message to eNB1 in operation 1213.

Upon receipt of the direct communication response message includinginformation about the cell or eNB of UE B from the MME in operation1207, eNB1 assigns a Tx index and an Rx index to UE B and transmits theassigned Tx index and Rx index of UE B and the C-RNTI of UE B in adirect communication response message to UE B in operation 1211. Only ifthe C-RNTI is newly assigned to UE B, eNB1 may include the C-RNTI of UEB. If a C-RNTI has not been assigned to UE B yet, eNB1 may assign aC-RNTI to UE B. Further, eNB1 may transmit other parameters related todirect communication in the direct communication response message to UEB. Upon receipt of the direct communication response message, UE Btransmits a direct communication complete message to eNB1 in operation1215.

A UE may maintain a Tx index and an Rx index. That is, the UE may assigna Tx index and an Rx index for its connection to another UE and transmitinformation about the assigned Tx index and Rx index to an eNB duringdirect connection setup. The eNB stores the information and uses it fortransmitting a PDCCH to the UE. The Tx index and Rx index managed by theUE may be transmitted in a direct communication request message or adirect communication complete message to the eNB. The property of a Txindex and an Rx index is the same irrespective of whether they areassigned by the eNB or the UE. If the eNB assigns a Tx index and an Rxindex, the eNB should maintain the Tx index and the Rx index. If the UEassigns a Tx index and an Rx index, the UE should maintain the Tx indexand the Rx index, thereby reducing the load of the eNB.

FIG. 13 illustrates another method for allocating a transmission indexand a reception index in allocating resources for D2D communicationwithin a cell according to an embodiment of the present disclosure.

Referring to FIG. 13, UE A has discovered UE B. When UE A wants toestablish a D2D connection with UE B, UE A triggers direct connectionsetup and transmits a direct communication request message including itsUE ID to UE B in operation 1301. According to an embodiment, the UE IDmay be an ID assigned to the UE for ProSe communication (that is, aProSe UE ID). Or the UE ID may be an idle mode ID assigned to the UE(that is, an S-TMSI). Or the UE ID may be a GUTI assigned to the UE. IfUE B accepts the direct communication request from UE A, UE B transmitsa direct communication response message including its UE ID to UE A inoperation 1303. UE A and UE B transmit direct communication requestmessages respectively to an eNB in operations 1305 and 1307. The directcommunication request messages may include the UE IDs of UE A and UE B.The order of operations 1305 and 107 may be changed. Upon receipt of thedirect communication request message from UE A, the eNB verifies thedirect communication request message, assigns a Tx index and an Rx indexto UE A, and transmits the assigned Tx index and Rx index of UE A andthe C-RNTI of UE A in a direct communication response message to UE A inoperation 1309. Only if the C-RNTI is newly assigned to UE A, the eNBmay include the C-RNTI of UE A. If a C-RNTI has not been assigned to UEA yet, the eNB may assign the C-RNTI to UE A. Further, the eNB maytransmit other parameters related to direct communication in the directcommunication response message to UE A. Upon receipt of the directcommunication response message, UE A transmits a direct communicationcomplete message to the eNB in operation 1313.

Likewise, upon receipt of the direct communication request message fromUE B, the eNB verifies the direct communication request message, assignsa Tx index and an Rx index to UE B, and transmits the assigned Tx indexand Rx index of UE B and the C-RNTI of UE B in a direct communicationresponse message to UE B in operation 1311. Only if the C-RNTI is newlyassigned to UE B, the eNB may include the C-RNTI of UE B. If a C-RNTIhas not been assigned to UE B yet, the eNB may assign the C-RNTI to UEB. Further, the eNB may transmit other parameters related to directcommunication in the direct communication response message to UE B. Uponreceipt of the direct communication response message, UE B transmits adirect communication complete message to the eNB in operation 1315. UE Aand UE B operate for D2D communication.

A UE may maintain a Tx index and an Rx index. That is, the UE may assigna Tx index and an Rx index for its connection to another UE and transmitinformation about the assigned Tx index and Rx index to an eNB duringdirect connection setup. The eNB stores the information and uses it fortransmitting a PDCCH to the UE. The Tx index and the Rx index managed bythe UE may be transmitted in a direct communication request message or adirect communication complete message to the eNB. The property of a Txindex and an Rx index are same irrespective of whether they are assignedby the eNB or the UE. If the eNB assigns a Tx index and an Rx index, theeNB should maintain the Tx index and the Rx index. If the UE assigns aTx index and an Rx index, the UE should maintain the Tx index and the Rxindex, thereby reducing the load of the eNB.

A method for using a connection index instead of a Tx index and an Rxindex to identify a transmitting UE and a receiving UE in the respectivecases where a UE is allocated Tx resources and Rx resources respectivelywill be described below.

A connection index is assigned to each UE at the time of directconnection setup and is unique across a plurality of connections of theUE with other UEs. The connection index is maintained for each UEindependently. The connection index of a UE identifies a transmitting UEor a receiving UE from among a plurality of UEs. If UE1 is connected toUE2 and UE3, connection index 0 may be assigned to UE1 for theconnection between UE1 and UE2, and connection index 1 may be assignedto UE1 for the connection between UE1 and UE3.

Each UE may be connected to a plurality of UEs. In the case where Rxresources are allocated to the UE, the UE needs to determine from whichUE it has to receive data in the allocated resources. For this purpose,the UE may use a connection index. For example, if UE1 is connected toUE2 and UE3 and Rx resources are allocated to UE1, UE1 may receive datafrom UE2 and UE3. Connection index 0 may be assigned to UE 1 for theconnection between UE1 and UE2 and connection index 1 for the connectionbetween UE1 and UE3. UE1 receives a control channel with its C-RNTI. Ifa Tx/Rx indicator is set to 0, UE1 receives data in resources indicatedby the control channel. Also, UE1 may identify a transmitting UE using aconnection index included in the control channel. The connection indexmay be included as an information field in the control channel or may beincluded in a CRC mask of the control channel.

In the case where a UE is connected to a plurality of UEs and Txresources are allocated to the UE, the UE needs to determine to which UEit has to transmit in the allocated resources. For this purpose, the UEmay use a connection index. For example, if UE1 is connected to UE2 andUE3 and Tx resources are allocated to UE1, UE1 may transmit data to UE2and UE3. Connection index 0 may be assigned to UE 1 for the connectionbetween UE1 and UE2 and connection index 1 for the connection betweenUE1 and UE3. UE1 receives a control channel with its C-RNTI. If a Tx/Rxindicator is set to 1, UE1 transmits data in resources indicated by thecontrol channel. Also, UE1 may identify a receiving UE using aconnection index included in the control channel. The connection indexmay be included as an information field in the control channel or may beincluded in a CRC mask of the control channel.

A UE may maintain a connection index. That is, the UE may assign aconnection index for its connection with another UE and transmitinformation about the connection index to an eNB during directconnection setup. The eNB stores this information and uses it fortransmitting a PDCCH to the UE. The connection index managed by the UEmay be transmitted to the eNB in a direct communication request messageor a direct communication complete message. The property of a connectionindex is the same irrespective of whether it is assigned by the eNB orthe UE. If the eNB assigns a connection index, the eNB should maintainthe connection index. If the UE assigns a connection index, the UEshould maintain the connection index, thereby reducing the load of theeNB.

A connection index is allocated in the same manner illustrated in FIGS.6 to 13, except that the connection index is used instead of a Tx indexand an Rx index in the embodiment of the present disclosure.

FIGS. 14 and 15 are diagrams illustrating signal flows for allocating aconnection index instead of a Tx index or an Rx index for D2Dcommunication according to an embodiment of the present disclosure.

Referring to FIG. 14, during D2D connection setup, eNB1 assignsconnection index p (Connection_idx=p) to UE A, for communication with UEB and eNB2 assigns connection index q (Connection_idx=q) to UE B, forcommunication with UE A in operation 1401. Operation 1403 is identicalto operation 605 of FIG. 6 except that a connection index is transmittedinstead of a Tx index on PDCCH1. Also, operation 1405 is identical tooperation 611 of FIG. 6 except that a connection index is transmittedinstead of an Rx index on PDCCH2. Operations 1407 and 1409 are identicalto operations 609 and 615 of FIG. 6 respectively except that data istransmitted and received to and from UE B corresponding to theconnection index instead of the Tx or Rx index. The other operations,such as transmission of a packet from UE A to UE B in resources X inoperation 1411, are performed in the same manner as their counterpartsillustrated in FIG. 6 and thus will not be described herein in detail.

Referring to FIG. 15, during D2D connection setup, eNB1 assignsconnection index p (Connection_idx=p) to UE A, for communication with UEB and eNB2 assigns connection index q (Connection_idx=q) to UE B, forcommunication with UE A in operation 1501. Operation 1503 is identicalto operation 705 of FIG. 7 except that a connection index is transmittedinstead of an Rx index on PDCCH4. Also, operation 1505 is identical tooperation 711 of FIG. 7 except that a connection index is transmittedinstead of a Tx index on PDCCH3. Operations 1507 and 1509 are identicalto operations 709 and 715 of FIG. 7 respectively, except that data istransmitted and received to and from UE B corresponding to theconnection index instead of the Tx or Rx index. The other operations,such as transmission of a packet from UE B to UE A in resources Y inoperation 1511, are performed in the same manner as their counterpartsillustrated in FIG. 7 and thus will not be described herein in detail.

Embodiment 3

In another embodiment of the present disclosure, resource information isindicated to both UEs of UE pair using single control channeltransmission by eNB. In this embodiment it is assumed that both UEs ofUE pair is connected with same eNB. Tx resources and Rx resources areidentified using UE Pair C-RNTI and UE-Idx for direct communication.

In this embodiment, a UE-pair C-RNTI, C-RNTI_(UE-pair) is assigned toeach UE pair participating in D2D communication in addition to a C-RNTIassigned to each UE to distinguish UEs belonging to the same eNB.Therefore, a plurality of UE-pair C-RNTIs are assigned to a UEparticipating in D2D communication with a plurality of UEs. A UE-pairC-RNTI is assigned during direct communication path setup and releasedupon release or termination of the path.

FIG. 16 illustrates an example of allocating C-RNTIs and UE-pair C-RNTIsaccording to an embodiment of the present disclosure.

Referring to FIG. 16, C-RNTI x, C-RNTI y, C-RNTI z, and C-RNTI a areassigned to UEx, UEy, UEz, and UEa, respectively, for communication withan eNB. UE-pair C-RNTIs, C-RNTI_(UE-pair-pq), C-RNTI_(UE-pair-ab) andC-RNTI_(UE-pair-ac) are assigned to a connection between UEp and UEq, aconnection between UEa and UEb, and a connection between UEa and UEc,respectively.

The eNB assigns a UE-pair C-RNTI from an address space from which itassigns C-RNTIs to other UEs communicating with it. This means thatC-RNTIs assigned to UEs communicating with the eNB and UE-pair C-RNTIsassigned to UE pairs are distinct.

A UE-pair C-RNTI assigned to a UE pair distinguishes D2D communicationbetween the UE pair from communication between a UE and an eNB. TheUE-pair C-RNTI also distinguishes D2D communication between the UE pairfrom communication between a UE of the UE pair and the eNB. The UE-pairC-RNTI also distinguishes communication between the UE pair fromcommunication between another UE pair.

If selective DL subframes and/or UL subframes are signaled or reservedfor only direct communication, C-RNTIs for UEs communicating with an eNBand UE-pair C-RNTIs for UE pairs may be assigned from independentaddress spaces having the same addresses. This is possible if the UEscommunicating with the eNB are aware of these selective subframes. Thismeans that the C-RNTIs assigned to the UEs communicating with the eNBand the UE-pair C-RNTIs assigned to the UE pairs may be same.

FIG. 17 illustrates an example of reusing a C-RNTI address space forUE-pair C-RNTIs according to an embodiment of the present disclosure.

Referring to FIG. 17, C-RNTI 1 and C-RNTI 2 are assigned to UE1 and UE2,respectively, for communicating with an eNB. Selective UL subframes arereserved for D2D communication. UE1 and UE2 use the assigned C-RNTIs toreceive and decode PDCCHs in DL subframes, DL SF n and DL SF n+1 toreceive information about resources for transmitting data in ULsubframes, UL SF n+2 and UL SF n+3 respectively. The UEs of UE pair xuse C-RNTI 1 in a DL subframe, DL SF n+2 to receive information aboutresources for D2D communication in a UL subframe, UL SF n+4. UE1 doesnot use C-RNTI 1 in the DL subframe, DL SF n+2 to receive informationabout resources for transmitting in the UL subframe, UL SF n+4. However,UE1 may use C-RNTI 1 in the DL subframe, DL SF n+2 to receiveinformation about resources for receiving DL packets in a DL subframe,DL SF n+3.

A description will be given of a method for signaling resourceallocation using a UE-pair C-RNTI.

If a UE wants to transmit data on a D2D communication link, the UEtransmits, to an eNB, a D2D BSR requesting resources for D2Dcommunication. An LCID distinguishes the D2D BSR from a normal BSR. TheLCID may be reserved to indicate the D2D BSR and included in the D2DBSR. Alternatively, the LCID may be included in a MAC subheaderindicating a MAC control element having the D2D BSR in a MAC PDU. TheD2D BSR may also include a destination ID. The destination ID is the IDof a destination to which the UE wants to transmit a signal through theD2D communication link. The destination ID may be a unicast address of aUE, a group cast address of group of UEs, or a broadcast address.

If PUCCH resources are available for transmission of the D2D BSR, theresources for the D2D BSR may be obtained using a general method such astransmitting a scheduling request to the eNB or by transmitting a randomaccess preamble to the eNB on an RACH.

FIGS. 18A and 18B illustrate methods for allocating resources fortransmission of a D2D BSR according to an embodiment of the presentdisclosure More specifically, FIG. 18A illustrates an example ofrequesting resources for transmitting a D2D BSR on a PUCCH and FIG. 18Billustrates an example of requesting resources for transmitting a D2DBSR on an RACH.

Upon receipt of the D2D BSR, the eNB allocates resources for D2Dtransmission and transmits a grant for D2D transmission on a PDCCH orEPDCCH in a DL subframe corresponding to a UL subframe reserved for D2Dcommunication. A control information format carrying the D2D resourceinformation is the same as or different from a control informationformat carrying resource information for transmission of a UE to an eNB.The PDCCH or EPDCCH is masked with a UE Pair C-RNTI. The PDCCH or EPDCCHtransmitted by eNB is received by the UE which has send D2D BSR as wellas the other UE which is communicating with the UE which has sent D2DBSR.

The eNB signals resources for direct communication between a UE pair ona PDCCH/EPDCCH masked with a UE-pair C-RNTI. The DL control region (thatis, the PDCCH/EPDCCH) indicates resources for direct communication aswell as resources for communication with the eNB. The resources fordirect communication are indicated to the UEs of the UE pair by a singletransmission. Resources are not indicated separately to each UE of theUE pair.

Resources may be allocated for each packet transmission on DL. Theresources may also be allocated in a semi-static manner so that theallocated resources are valid during a plurality of TTIs. The resourcesmay also be allocated in a static manner so that the determinedresources are valid for the duration of a connection between the UEs.

A UE that performs direct communication with another UE monitors a DLcontrol region for resource allocation using a UE-pair C-RNTI. A UE of aUE pair communicating with an eNB as well as with another UE monitors aDL control region for resource allocation using a C-RNTI and a UE-pairC-RNTI. If selective subframes are signaled or reserved for only directcommunication, the UE of the UE pair monitors the DL control region forresource allocation of the selective subframes for direct communicationin respective DL subframes only using the UE-pair C-RNTI. However, ifthe selective subframes are UL subframes, the UE may monitor these DLsubframes using the C-RNTI assigned for communication with the eNB forDL resource allocation. If the selective subframes are DL subframes, theUE may monitor these DL subframes using the C-RNTI assigned forcommunication with the eNB for UL resource allocation. If the UE is alsocommunicating with the eNB, the UE monitors the DL control region forDL/UL resource allocation using the C-RNTI assigned for communicationwith the eNB in other DL subframes.

FIG. 19 illustrates an example of distinguishing resources forcommunication between a UE pair from resources of other UEs in thecoverage area of an eNB according to an embodiment of the presentdisclosure.

Referring to FIG. 19, UE1 and UE2 participate in direct communicationusing the UL frequency F2. UE3 is communicating with the eNB using theUL frequency F2. UE3 monitors the DL subframe, DL SF n using a C-RNTIwhereas the UE1-UE2 pair monitors the DL subframe, DL SF n using aUE-pair C-RNTI, C-RNTI_(UE-pair). In FIG. 19, a control region of the DLsubframe DL SF n indicates resources for the UL subframe UL SF n+3. TheC-RNTI of UE3 and the UE-pair C-RNTI of the UE1-UE2 pair distinguish aPDCCH and UL resources for UE3 from a PDCCH and UL resources for theUE1-UE2 pair.

FIG. 20 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for communication betweena UE of the UE pair and an eNB according to an embodiment of the presentdisclosure.

Referring to FIG. 20, UE1 and UE2 participate in direct communicationusing the UL frequency F2. UE1 is also communicating with the eNB usingthe UL frequency F2. UE1 monitors the DL subframe DL SF n using a C-RNTIand a UE-pair C-RNTI. In FIG. 20, the control region of the DL subframeDL SF n indicates resources for the UL subframe UL SF n+3. The C-RNTI ofUE1 and the UE-pair C-RNTI of the UE1-UE2 pair distinguish a PDCCH andUL resources for UE1 for direct communication with UE2 from a PDCCH andUL resources for communication with the eNB.

FIG. 21 illustrates an example of distinguishing resources forcommunication between one UE pair from resources for communicationbetween another UE pair according to an embodiment of the presentdisclosure.

Referring to FIG. 21, UE1 and UE2 participate in direct communicationusing the UL frequency F2, and UE3 and UE4 participate in directcommunication using the UL frequency F2. UE1 and UE2 of the UE1-UE2 pairmonitor the DL subframe DL SF n using their UE-pair C-RNTI, whereas UE3and UE4 of the UE3-UE4 pair monitor the DL subframe DL SF n using theirUE-pair C-RNTI. In FIG. 21, the control region of the DL subframe DL SFn indicates resources for the UL subframe UL SF n+3. The UE-pair C-RNTIof the UE1-UE2 pair and the UE-pair C-RNTI of the UE3-UE4 pairdistinguish a PDCCH and UL resources for the UE1-UE2 pair from a PDCCHand UL resources for the UE3-UE4 pair.

Resources for direct communication are signaled to the UEs of a UE pairby a single transmission using a UE-pair C-RNTI assigned to the UE pair.However, upon receipt of the signal using the UE-pair C-RNTI, each UE ofthe UE pair does not know whether to transmit or receive in theresources. Accordingly, a method for identifying Tx resources and Rxresources when a UE-pair C-RNTI is used will be described below.

In unidirectional communication, Tx and Rx roles between the UEs of a UEpair are predetermined or indicated by direct path setup signaling. Forexample, for the UE1-UE2 pair, UE1 may be a transmitter and UE2 may be areceiver. The eNB signals resources for the UE1-UE2 pair using theUE-pair C-RNTI assigned to the UE1-UE2 pair. Both UE1 and UE2 receiveresource allocation information in a DL control region using the UE-pairC-RNTI of the UE1-UE2 pair. UE1 and UE2 receive the same PDCCH and usethe allocated resources according to their Tx and Rx roles determined atthe time of direct path setup. That is, UE1 uses the allocated resourcesfor transmission and UE2 uses the allocated resources for reception.

FIG. 22 illustrates a method for identifying Tx resources and Rxresources in the case of unidirectional communication according to anembodiment of the present disclosure.

Referring to FIG. 22, UE1 and UE2 receive resource information fordirect communication by receiving and decoding a PDCCH using a UE pairC-RNTI assigned to the UE1-UE2 pair. UE1 transmits data to UE2 inallocated resources whereas UE2 receives data from UE1 in the allocatedresources.

In bidirectional communication, each UE of a UE pair plays Tx and Rxroles. An eNB assigns a 1-bit UE index (UE_idx) to each of the UEs ofthe UE pair in addition to a UE-pair C-RNTI. For example, for theUE1-UE2 pair, UE_idx 0 is assigned to UE 1 and UE_idx 1 is assigned toUE2. The eNB transmits resources for the UE1-UE2 pair using the UE-pairC-RNTI assigned to the UE1-UE2 pair. The eNB adds the UE index of a UEin the resource allocation signaling. The UE index identifies a UE whichhas to use the allocated resources for transmission. The UE index may beused in CRC masking of a PDCCH or may be included as an informationfield in the decoded PDCCH. UE1 and UE2 receive the same PDCCH and usethe allocated resources according to the UE indexes assigned by thenetwork at the time of direct path setup.

FIG. 23 illustrates a method for identifying Tx resources and Rxresources in the case of bidirectional communication according to anembodiment of the present disclosure.

Referring to FIG. 23, if UE1 receives and decodes a PDCCH using theUE-pair C-RNTI and the UE index of UE1 is included in the PDCCH, UE1transmits data in allocated resources. As UE1 receives and decodes aPDCCH in the DL subframe DL SF n using the UE-pair C-RNTI and the UEindex of UE1 is included in the PDCCH, UE1 transmits data in allocatedresources of the UL subframe UL SF n+3. If UE2 receives and decodes aPDCCH using the UE-pair C-RNTI and the UE index of UE2 is included inthe PDCCH, UE2 transmits data in allocated resources. As UE2 receivesand decodes a PDCCH in the DL subframe DL SF n+2 using the UE-pairC-RNTI and the UE index of UE2 is included in the PDCCH, UE2 transmitsdata in allocated resource of the UL subframe UL SF n+5.

To identify Tx resources and Rx resources in bidirectional communicationin which both UEs of a UE pair play Tx and Rx roles, the eNB may assigntwo UE-pair C-RNTIs to the UEs of the UE pair. For example, if UE1operates as a transmitter, a UE-pair C-RNTI, C-RNTI_(UE-pair 1) may beassigned to UE1 and if UE1 operates as a receiver, a UE-pair C-RNTI,C-RNTI_(UE-pair 2) may be assigned to UE1. If UE2 operates as areceiver, the UE-pair C-RNTI, C-RNTI_(UE-pair 1) may be assigned to UE2and if UE2 operates as a transmitter, the UE-pair C-RNTI,C-RNTI_(UE-pair 2) may be assigned to UE2. The eNB transmits resourcesfor the UE1-UE2 pair using one of the UE-pair C-RNTIs assigned to theUE1-UE2 pair. If UE1 should transmit data in allocated resources and UE2should receive the data in the allocated resources, the eNB uses theUE-pair C-RNTI, C-RNTI_(UE-pair 1). If UE2 should transmit data inallocated resources and UE1 should receive the data in the allocatedresources, the eNB uses the UE-pair C-RNTI, C-RNTI_(UE-pair 2). UE1 andUE2 receive the same PDCCH and use allocated resources according to theUE-pair C-RNTIs assigned by the network at the time of direct pathsetup.

FIG. 24 illustrates a method for identifying Tx resources and Rxresources in the case of bidirectional communication according to anembodiment of the present disclosure.

Referring to FIG. 24, if UE1 receives and decodes a PDCCH in the DLsubframe DL SF n using the UE-pair C-RNTI C-RNTI_(UE-pair 1) which is aC-RNTI assigned to UE1 for transmission, UE1 transmits data in allocatedresources of the UL subframe UL SF n+3. If UE2 receives and decodes aPDCCH in the DL subframe DL SF n+2 using the UE-pair C-RNTIC-RNTI_(UE-pair 1) which is a C-RNTI assigned to UE2 for reception, UE2receives data in allocated resources of the UL subframe UL SF n+5. IfUE2 receives and decodes a PDCCH in the DL subframe DL SF n+2 using theUE-pair C-RNTI C-RNTI_(UE-pair 2) which is a C-RNTI assigned to UE2 fortransmission, UE2 transmits data in allocated resources of the ULsubframe UL SF n+5. If UE1 receives and decodes a PDCCH in the DLsubframe DL SF n+2 using the UE-pair C-RNTI C-RNTI_(UE-pair 2) which isa C-RNTI assigned to UE1 for reception, UE1 receives data in allocatedresources of the UL subframe UL SF n+5.

A UE-pair C-RNTI may be used together with a UE index in a measurementreport, a BSR, a resource request, and the like transmitted to an eNB.The eNB may then uniquely identify a UE and a communication link of theUE for which the report or request is transmitted. Similarly, the eNBmay use the UE-pair C-RNTI in DL signaling to the UE. If the measurementreport, the BSR, the resource request, and the like are for acommunication link between the UE and the eNB, the UE transmits themeasurement report, the BSR, the resource request, and the like to theeNB using a C-RNTI assigned for communication with the eNB. If themeasurement report, the BSR, the resource request, and the like are forcommunication between the UEs of the UE pair, the UE transmits themeasurement report, the BSR, the resource request, and the like to theeNB using the UE-pair C-RNTI together with the UE index.

If two UE-pair C-RNTIs are assigned to a UE pair, a UE of the UE pairmay use the UE-pair C-RNTIs for transmitting in a measurement report, aBSR, a resource request, and the like to the eNB. If the measurementreport, the BSR, the resource request, and the like are for acommunication link between the UE and the eNB, the UE transmits themeasurement report, the BSR, the resource request, and the like to theeNB using a C-RNTI assigned for communication with the eNB. If themeasurement report, the BSR, the resource request, and the like are forcommunication between the UEs of the UE pair, the UE transmits themeasurement report, the BSR, the resource request, and the like to theeNB using the two UE-pair C-RNTIs. The eNB may then uniquely identifythe UE and the communication link of the UE for which the reports orrequest is transmitted. Similarly, the eNB may use the two UE-pairC-RNTIs in DL signaling to the UEs of the UE pair.

Now a description will be given of a method for allocating a UE indexand a UE-pair C-RNTI.

FIG. 25 illustrates a method for allocating a UE index (UE_idx) and aUE-pair C-RNTI (C-RNTI_(UE-pair)) in allocating resources for D2Dcommunication within a cell according to an embodiment of the presentdisclosure.

Referring to FIG. 25, UE A and UE B transmit direct communicationrequest messages to an eNB in operations 2501 and 2502. Each of UE A andUE B includes the UE ID of the UE B and the UE ID of UE A in the directcommunication request message. The order of the transmissions of thedirect communication request messages from UE A and UE B to the eNB maybe changed. One UE may acquire the UE ID of the other UE with which itwants to communicate in the following manner.

UE A initiates direct communication setup with UE B on a D2Dcommunication link. UE A transmits a direct communication requestmessage including its UE ID. The UE ID may be an ID of the UE specificto D2D communication or may be some other UE ID which identifies the UE.The UE ID may also be an application user ID of the UE. If UE B acceptsthe communication request from UE A, UE B transmits a directcommunication response message including its UE ID to UE A. UE A and UEB may know each other's UE ID as a part of a discovery message. UE A andUE B may periodically transmit discovery messages. The UE IDs of UEswith which the UE wants to communicate may be preconfigured in the UE.

Upon receipt of the direct communication request message from UE A, theeNB verifies the direct communication request message and then assignsC-RNTI_(UE-pair-ab) as a UE-pair C-RNTI and UE_idx 0 as a UE index to UEA. The eNB transmits the assigned C-RNTI_(UE-pair) and UE_idx to UE A ina direct communication response message in operation 2503. The eNB maytransmit other parameters related to direct communication in the directcommunication response message. Upon receipt of the direct communicationrequest message from UE B, the eNB verifies the direct communicationrequest message and then assigns C-RNTI_(UE-pair-ab) and UE_idx 1 as aUE index to UE B. The eNB sends the assigned C-RNTI_(UE-pair) and UE_idxto UE B in a direct communication response message in operation 2504.The eNB may transmit other parameters related to direct communication inthe direct communication response message. Upon receipt of the directcommunication response messages, UE A and UE B transmit directcommunication complete messages to the eNB respectively in operations2505 and 2506. UE A and UE B perform operations using the assignedUE-pair C-RNTI and UE indexes. UE A and UE B monitor a PDCCH or anEPDCCH using the UE-pair C-RNTI, C-RNTI_(UE-pair-ab) in operations 2507and 2508. This monitoring may be added to monitoring a PDCCH or anEPDCCH using C-RNTIs assigned to UE A and UE B for UE-eNB communication.

If UE A wants to transmit data to UE B on the D2D communication link, UEA transmits a D2D BSR to the eNB in operation 2511. The D2D BSR includesthe ID of UE B or the UE-pair C-RNTI, C-RNTI_(UE-pair-ab). Upon receiptof the D2D BSR, the eNB transmits a grant in a PDCCH or EPDCCH maskedwith the UE-pair C-RNTI, C-RNTI_(UE-pair-ab) and a UE index inoperations 2512 and 2513. The PDCCH or EPDCCH may be received by both UEA and UE B. As the UE index corresponds to UE A, UE A transmits data inallocated resources in operation 2514 and UE B receives the data in theallocated resources in operation 2515. The UE-pair C-RNTI,C-RNTI_(UE-pair-ab) indicates that the resources are for communicationbetween UE A and UE B.

If UE B wants to transmit data to UE A on the D2D communication link, UEB transmits a D2D BSR to the eNB in operation 2521. The D2D BSR includesthe ID of UE A or the UE-pair C-RNTI, C-RNTI_(UE-pair-ab). Upon receiptof the D2D BSR, the eNB transmits a grant in a PDCCH/EPDCCH masked withthe UE-pair C-RNTI, C-RNTI_(UE-pair-ab) and a UE index in operations2522 and 2523. The PDCCH or EPDCCH may be received by both UE A and UEB. As the UE index corresponds to UE B, UE B transmits data in allocatedresources in operation 2524 and UE A receives the data in the allocatedresources in operation 2525. The UE-pair C-RNTI C-RNTI_(UE-pair-ab)indicates that the resources are for communication between UE A and UEB.

If both unidirectional communication and bidirectional communication aresupported, the eNB may assign a UE index only in the case ofbidirectional communication. A UE may indicate to the eNB whether thecommunication is bidirectional or unidirectional in a directcommunication request message.

FIG. 26 is a diagram illustrating a signal flow for allocating a TxUE-pair C-RNTI and an Rx UE-pair C-RNTI according to an embodiment ofthe present disclosure.

Referring to FIG. 26, UE A and UE B transmit direct communicationrequest messages to the eNB respectively in operations 2601 and 2602.Each of UE A and UE B includes the UE ID of the UE B and the UE ID of UEA in its direct communication request message. The order of thetransmissions of the direct communication request messages from UE A andUE B to the eNB may be changed. One UE may acquire the UE ID of theother UE with which it wants to communicate in the following manner.

UE A initiates direct communication setup with UE B on a D2Dcommunication link. UE A transmits a direct communication requestmessage including its UE ID. The UE ID may be an ID of the UE specificto D2D communication or may be some other UE ID which identifies the UE.The UE ID may also be an application user ID of the UE. If UE B acceptsthe communication request from UE A, UE B transmits a directcommunication response message including its UE ID to UE A. UE A and UEB may know each other's UE ID as a part of a discovery message. UE A andUE B may periodically transmit discovery messages. The UE IDs of UEswith which the UE wants to communicate may be preconfigured in the UE.

Upon receipt of the direct communication request message from UE A, theeNB verifies the direct communication request message and assigns a TxUE-pair C-RNTI, C-RNTI_(UE-pair-1) and an Rx UE-pair C-RNTI,C-RNTI_(UE-pair-2) to UE A. The eNB transmits the assigned Tx UE-pairC-RNTI and Rx UE-pair C-RNTI to UE A in a direct communication responsemessage in operation 2603. The eNB may transmit other parameters relatedto direct communication in the direct communication response message.

Upon receipt of the direct communication request message from UE B, theeNB verifies the direct communication request message and assigns a TxUE-pair C-RNTI, C-RNTI_(UE-pair-2) and an Rx UE-pair C-RNTI,C-RNTI_(UE-pair-1) to UE B. The eNB sends the assigned Tx and Rx UE-pairC-RNTIs to UE B in a direct communication response message in operation2604. The eNB may transmit other parameters related to directcommunication in the direct communication response message.

Upon receipt of the direct communication response messages, UE A and UEB transmit direct communication complete messages to the eNB,respectively in operations 2605 and 2606. UE A and UE B performoperations using the assigned Tx and Rx UE-pair C-RNTIs. UE A and UE Bmonitor a PDCCH or an EPDCCH using the UE-pair C-RNTIs,C-RNTI_(UE-pair-1) and C-RNTI_(UE-pair-2) in operations 2607 and 2608.This monitoring may be added to monitoring a PDCCH/EPDCCH using C-RNTIsassigned to UE A and UE B for UE-eNB communication.

If UE A wants to transmit data to UE B on the D2D communication link, UEA transmits a D2D BSR to the eNB in operation 2611. The D2D BSR includesthe ID of UE B or the UE-pair C-RNTI, C-RNTI_(UE-pair-1) orC-RNTI_(UE-pair-2). Upon receipt of the D2D BSR, the eNB transmits agrant in a PDCCH or EPDCCH masked with the UE-pair C-RNTI,C-RNTI_(UE-pair-1) in operations 2612 and 2613. The PDCCH or EPDCCH maybe received by both UE A and UE B. As the UE-pair C-RNTI,C-RNTI_(UE-pair-1) corresponds to the Tx UE-pair C-RNTI of UE A, UE Atransmits data in allocated resources in operation 2614 and UE Breceives the data in the allocated resources in operation 2615.

If UE B wants to transmit data to UE A on the D2D communication link, UEB transmits a D2D BSR to the eNB in operation 2621. The D2D BSR includesthe ID of UE A or the UE-pair C-RNTI, C-RNTI_(UE-pair-1) orC-RNTI_(UE-pair-2). Upon receipt of the D2D BSR, the eNB transmits agrant in a PDCCH or EPDCCH masked with the UE-pair C-RNTI,C-RNTI_(UE-pair-2) in operations 2622 and 2623. The PDCCH or EPDCCH maybe received by both UE A and UE B. As the UE-pair C-RNTI,C-RNTI_(UE-pair-2) corresponds to the Tx UE-pair C-RNTI of UE B, UE Btransmits data in allocated resources in operation 2624 and UE Areceives the data in the allocated resources in operation 2625.

While UL subframes are used for direct communication in the foregoingdrawings, the present disclosure is equally applicable for the cases inwhich DL subframes or both DL and UL subframes are used for directcommunication. The present disclosure is also applicable to a systemoperating in Frequency Division Duplexing (FDD) mode or Time DivisionDuplexing (TDD) mode.

A C-RNTI assigned to a UE Pair may be a UE-pair C-RNTI, asemi-persistently scheduled UE-pair C-RNTI, or a temporary UE-pair. Inan embodiment in which two UE-pair C-RNTIs are assigned to a UE pair,one may be semi-persistently scheduled and the other may be normallyscheduled. In another embodiment in which one UE-pair C-RNTI is assignedto a UE pair, it may be semi-persistently or normally scheduled.

Embodiment 4

A third embodiment of the present disclosure provides a method foridentifying Tx resources and Rx resources using one C-RNTI reserved forD2D communication, UE pair ID and UE_Idx. In this embodiment resourceinformation is indicated to both UEs of UE pair using single controlchannel transmission by eNB. In this embodiment it is assumed that bothUEs of UE pair is connected with same eNB.

In the third embodiment of the present disclosure, to distinguish one UEfrom another UE served by the same eNB, one C-RNTI is reserved asC-RNTI_(UE-pairs) from a C-RNTI space assigned to each UE. The C-RNTIspace from which C-RNTI_(UE-pairs) is reserved is the same address spacefrom which UEs communicating with the eNB are assigned C-RNTIs. Thereserved C-RNTI is used to distinguish resources assigned to a UE(s) forcommunicating with the eNB from resources assigned to UE pairs fordirect communication. Each UE pair engaged in direct communication isassigned a UE pair ID. A UE pair ID distinguishes one UE pair fromanother UE pair. A UE engaged in direct communication with a pluralityof UEs is assigned a plurality of UE pair IDs. A UE pair ID is assignedby a network (for example, an eNB or MME) to each UE pair engaged indirect communication. A UE pair ID assigned to the UEs of a UE pair isadded to C-RNTIs assigned to the UEs for communication with the eNB bythe eNB. A UE pair ID is assigned during direct communication pathsetup. The UE pair ID is used to distinguish resources amongst UE pairs.Resources for all UE pairs are indicated using the reserved C-RNTI bythe eNB. The UE pair ID may be added in a message (for example, a fieldin control information) carrying resource information. The UE pair IDmay also be added in a CRC mask for a PDCCH.

A method for identifying a UE pair using a reserved C-RNTI and a UE pairID distinguishes UE pair communication from communication between otherUEs (i.e., UEs which are not involved in direct communication) and aneNB in the coverage area of the eNB. It also distinguishes UE paircommunication from communication between a UE of the UE pair with theeNB. It also distinguishes one UE pair communication from another UEpair communication.

A description will be given of a method for signaling resourceallocation using a reserved C-RNTI and a UE pair ID.

If a UE wants to transmit on a D2D communication link, the UE transmitsto an eNB a D2D BSR requesting resources for D2D communication. An LCIDmay distinguish the D2D BSR from a normal BSR. The LCID may be reservedto indicate the D2D BSR and included in the D2D BSR. Alternatively, theLCID may be included in a MAC subheader indicating a MAC control elementhaving the D2D BSR in a MAC PDU. The D2D BSR may also include adestination ID. The destination ID is the ID of a destination to whichthe UE wants to transmit a control and/or data packets through the D2Dcommunication link. The destination ID may be a unicast address of anUE, group cast address of a group of UEs, or broadcast address.

If PUCCH resources are available for transmission of the D2D BSR, theresources for the D2D BSR may be obtained using a general method such astransmitting a scheduling request to the eNB or by transmitting a randomaccess preamble to the eNB on an RACH.

Upon receipt of the D2D BSR, the eNB allocates resources for D2Dtransmission and transmits a grant for D2D transmission on a PDCCH orEPDCCH in a DL subframe corresponding to a UL subframe reserved for D2Dcommunication. The PDCCH or EPDCCH is masked with the reserved C-RNTI.The UE pair ID may be included as an information field in the PDCCH orEPDCCH. The PDCCH or EPDCCH transmitted by the eNB may be received byanother UE communicating with the UE transmitting the BSR as well as theUE transmitting the BSR. The eNB signals resources for directcommunication between a UE pair in a DL frequency. The DL control region(that is, the PDCCH or EPDCCH) indicates resources for directcommunication as well as resources for communication with the eNB. Theresources for direct communication are indicated to the UEs of the UEpair by a single transmission. Resources are not indicated separately toeach UE of the UE pair.

Resources may be allocated for each packet transmission on DL. Theresources may also be allocated in a semi-static manner so that theallocated resources are valid during a plurality of TTIs. The resourcesmay also be allocated in a static manner so that the determinedresources are valid for the duration of a connection between the UEs.

A UE that performs direct communication with another UE monitors the DLcontrol region for resource allocation using a reserved C-RNTI and a UEpair ID. A UE of a UE pair communicating with an eNB as well as withanother UE monitors the DL control region for resource allocation usinga C-RNTI, the reserved C-RNTI, and a UE pair ID. If selective subframes(DL, UL, or both DL and UL) are signaled or reserved for only directcommunication, the UEs of the UE pair monitor the DL control region forresource allocation of the selective subframes for direct communicationin respective DL subframes using the reserved C-RNTI and the UE pair ID.However, if the selective subframes are UL subframes, the UE may monitorthese DL subframes using a C-RNTI assigned for communication with theeNB, for DL resource allocation. If the selective subframes are DLsubframes, the UE may monitor these DL subframes using the C-RNTIassigned for communication with the eNB, for UL resource allocation. Ifthe UE is also communicating with the eNB, the UE monitors the DLcontrol region for DL/UL resource allocation using the C-RNTI assignedfor communication with the eNB in other DL subframes.

FIG. 27 illustrates an example of distinguishing resources forcommunication between a UE pair from resources of other UEs within thecoverage area of an eNB according to an embodiment of the presentdisclosure.

Referring to FIG. 27, UE1 and UE2 participate in direct communicationusing the UL frequency F2, and UE3 is communicating with the eNB usingthe UL frequency F2. UE3 monitors the DL subframe DL SF n using a C-RNTIwhereas the UE1 and UE2 monitor the DL subframe DL SF n using a reservedC-RNTI (C-RNTI_(UE-pairs)). In FIG. 27, a control region of the DLsubframe DL SF n indicates resources for the UL subframe UL SF n+3. TheC-RNTI of UE3 and the reserved C-RNTI distinguish PDCCHs and ULresources for UE3 and the UE1-UE2 pair.

FIG. 28 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for communication betweena UE of the UE pair and an eNB according to an embodiment of the presentdisclosure.

Referring to FIG. 28, UE1 and UE2 participate in direct communicationusing the UL frequency F2 and UE1 is also communicating with the eNBusing the UL frequency F2. UE1 monitors the DL subframe DL SF n using aC-RNTI and a reserved C-RNTI. In FIG. 28, a control region of the DLsubframe DL SF n indicates resources for the UL subframe UL SF n+3. TheC-RNTI of UE1 and the reserved C-RNTI distinguish PDCCHs and ULresources for UE1 for direct communication with UE2 and forcommunication with the eNB.

FIG. 29 illustrates an example of distinguishing resources forcommunication between one UE pair from resources for communicationbetween another UE pair according to an embodiment of the presentdisclosure.

Referring to FIG. 29, UE1 and UE2 participate in direct communicationusing the UL frequency F2, and UE3 and UE4 participate in directcommunication using the UL frequency F2. UE1 and UE2 of the UE1-UE2 pairmonitor the DL subframe DL SF n using their UE pair ID and a reservedC-RNTI. UE3 and UE4 of the UE3-UE4 pair monitor the DL subframe DL SF nusing their UE pair ID and the reserved C-RNTI. The reserved C-RNTI andUE pair ID of the UE1-UE2 pair, and the reserved C-RNTI and UE pair IDof the UE3-UE4 pair distinguish PDCCHs and UL resources for the UE1-UE2pair and the UE3-UE4 pair.

Resources for direct communication are signaled to the UEs of a UE pairby a single transmission using a reserved C-RNTI and a UE pair IDassigned to the UE pair. However, upon receipt of information about theresources using the reserved C-RNTI and the UE pair ID, each UE of theUE pair does not know whether to transmit or receive data in theresources. Accordingly, a method for identifying Tx resources and Rxresources when a reserved C-RNTI and a UE pair ID are used will bedescribed.

In unidirectional communication, Tx and Rx roles between the UEs of a UEpair are predetermined or indicated by direct path setup signaling. Forexample, for a UE1-UE2 pair, UE1 may be a transmitter and UE2 may be areceiver. An eNB transmits resources for the UE1-UE2 pair using areserved C-RNTI and a UE pair ID assigned to the UE1-UE2 pair. Both UE1and UE2 receive resource allocation information in a control region of aDL frequency using the reserved C-RNTI and the UE pair ID. UE1 and UE2receive the same PDCCH and use allocated resources according to their Txand Rx roles determined during the direct path setup. That is, UE1 usesthe allocated resources for transmission and UE2 uses the allocatedresources for reception.

In bidirectional communication, each UE of a UE pair plays Tx and Rxroles. The eNB assigns a 1-bit UE index (UE_idx) to each UE in additionto a UE pair ID. For example, for a UE1-UE2 pair, UE_idx=0 for UE1 andUE_idx=1 for UE2. The eNB signals resources for the UE1-UE2 pair using areserved C-RNTI and a UE pair ID assigned to the UE1-UE2 pair. The eNBadds the UE index to resource allocation signaling. The UE indexidentifies a UE to transmit data in the allocated resources. The UEindex may be used in CRC masking of a PDCCH or may be included as aninformation field in the decoded PDCCH. UE1 and UE2 receive the samePDCCH and use the allocated resources using their UE indexes assigned bythe network during direct path setup.

Or the eNB may assign two UE pair IDs to the UEs of the UE pair in orderto distinguish Tx resources from Rx resources in bidirectionalcommunication in which the UEs of the UE pair play the Tx and Rx roles.For example, if UE1 operates as a transmitter, UE pair ID 1 is assignedto UE1 and if UE1 operates as a receiver, UE pair ID 2 is assigned toUE1. If UE2 operates as a receiver, UE pair ID 1 is assigned to UE2 andif UE2 operates as a transmitter, UE pair ID 2 is assigned to UE2. TheeNB transmits resources for the UE1-UE2 pair using the reserved C-RNTIand one of the UE pair IDs assigned to the UE1-UE2 pair. If UE1 has touse allocated resources for transmission and UE2 has to receive usingthe allocated resources, the eNB uses the reserved C-RNTI and UE pairID 1. If UE2 has to use allocated resources for transmission and UE1 hasto receive using the allocated resources, the eNB uses the reservedC-RNTI and UE pair ID 2.

A UE pair ID may be used together with a UE index in a measurementreport, a BSR, a resource request, and the like transmitted to an eNB.The eNB may uniquely identify a UE and a communication link of the UEfor which the report or request is transmitted. Similarly, the eNB mayuse the UE pair ID in DL signaling to the UE. If the measurement report,the BSR, the resource request, and the like are for communicationbetween the UE and the eNB, the UE transmits the measurement report, theBSR, the resource request, and the like to the eNB using a C-RNTIassigned for communication with the eNB. If the measurement report, theBSR, the resource request, and the like are for direct communicationbetween the UEs of the UE pair, the UE transmits the measurement report,the BSR, the resource request, and the like to the eNB using the UE pairID together with a UE index.

If two UE pair IDs are assigned to a UE pair, a UE of the UE pair mayuse the two UE pair IDs for transmitting a measurement report, a BSR, aresource request, and the like to the eNB. If the measurement report,the BSR, the resource request, and the like are for communicationbetween the UE and the eNB, the UE transmits the measurement report, theBSR, the resource request, and the like to the eNB using a C-RNTIassigned for communication with the eNB. If the measurement report, theBSR, the resource request, and the like are for direct communicationbetween the UEs of the UE pair, the UE transmits the measurement report,the BSR, the resource request, and the like to the eNB using the two UEpair IDs. The eNB may then uniquely identify the UE and thecommunication link of the UE for which the reports or request istransmitted. Similarly, the eNB may use the two UE pair IDs in DLsignaling to the UE.

A description will be given of a method for allocating a UE index and aUE pair ID.

FIG. 30 illustrates a method for allocating UE index and a UE pair ID inallocating resources for D2D communication within a cell according to anembodiment of the present disclosure.

Referring to FIG. 30, UE A and UE B transmit direct communicationrequest messages to an eNB respectively in operations 3001 and 3002.Each of UE A and UE B includes the UE ID of the UE B and the UE ID of UEA in its direct communication request message. The order of thetransmissions of the direct communication request messages from UE A andUE B to the eNB may be changed. One UE may acquire the UE ID of anotherUE with which it wants to communicate in the following manner.

UE A initiates direct communication setup with UE B on a D2Dcommunication link. UE A transmits a direct communication requestmessage including its UE ID. The UE ID may be an ID of the UE specificto D2D communication or may be some other UE ID which identifies the UE.The UE ID may also be an application user ID of the UE. If UE B acceptsthe communication request from UE A, UE B transmits a directcommunication response message including its UE ID to UE A. UE A and UEB may know each other's UE ID as a part of a discovery message. UE A andUE B may periodically transmit discovery messages. The UE IDs of UEswith which the UE wants to communicate may be preconfigured in the UE.

Upon receipt of the direct communication request message from UE A, theeNB verifies the direct communication request message and then assignsUE pair ID=1 and UE_idx=0 to UE A. The eNB transmits the assigned UEpair ID and UE index to UE A in a direct communication response messagein operation 3003. The eNB may transmit other parameters related todirect communication in the direct communication response message. Uponreceipt of the direct communication request message from UE B, the eNBverifies the direct communication request message and then assigns UEpair ID=1 and UE_idx=1 to UE B. The eNB sends the assigned UE pair IDand UE index to UE B in a direct communication response message inoperation 3004. The eNB may transmit other parameters related to directcommunication in the direct communication response message.

Upon receipt of the direct communication response messages, UE A and UEB transmit direct communication complete messages to the eNB inoperations 3005 and 3006. UE A and UE B perform operations using theassigned UE pair ID and UE indexes. UE A and UE B monitor a PDCCH orEPDCCH using UE pair ID 1 and a reserved C-RNTI, C-RNTI_(UE-pairs) inoperations 3007 and 3008. This monitoring may be added to monitoring aPDCCH or EPDCCH using C-RNTIs assigned to UE A and UE B for UE-eNBcommunication.

If UE A wants to transmit data to UE B on the D2D communication link, UEA transmits a D2D BSR to the eNB in operation 3011. The D2D BSR includesthe ID of UE B or UE pair ID 1. Upon receipt of the D2D BSR, the eNBtransmits a grant in a PDCCH or EPDCCH masked with UE pair ID 1 and a UEindex in operations 3012 and 3013. The PDCCH or EPDCCH may be receivedby both UE A and UE B. As the UE index corresponds to UE A, UE Atransmits data in allocated resources in operation 3014 and UE Breceives data in the allocated resources in operation 3015. UE pair ID 1indicates that the resources are for communication between UE A and UEB.

If UE B wants to transmit data to UE A on the D2D communication link, UEB transmits a D2D BSR to the eNB in operation 3021. The D2D BSR includesthe ID of UE A or UE pair ID 1. Upon receipt of the D2D BSR, the eNBtransmits a grant in a PDCCH or EPDCCH masked with UE pair ID 1 and a UEindex in operations 3022 and 3023. The PDCCH or EPDCCH may be receivedby both UE A and UE B. As the UE index corresponds to UE B, UE Btransmits data in allocated resources in operation 3024 and UE Areceives data in the allocated resources in operation 3025. UE pair ID 1indicates that the resources are for communication between UE A and UEB.

If both unidirectional communication and bidirectional communication aresupported, the eNB may assign a UE index only in the case ofbidirectional communication. A UE may indicate to the eNB whether thecommunication is bidirectional or unidirectional in a directcommunication request message.

FIG. 31 illustrates an operation for allocating a Tx UE pair ID and anRx UE pair ID according to an embodiment of the present disclosure.

Referring to FIG. 31, UE A and UE B transmit direct communicationrequest messages to an eNB respectively in operations 3101 and 3102.Each of UE A and UE B includes the UE ID of the UE B and the UE ID of UEA in its direct communication request message. The order of thetransmissions of the direct communication request messages from UE A andUE B to the eNB may be changed. A UE may acquire the UE ID of another UEwith which it wants to communicate in the following manner.

UE A initiates direct communication establishment with UE B on a D2Dcommunication link. UE A transmits a direct communication requestmessage including its UE ID. The UE ID may be an ID of the UE specificto D2D communication or may be some other UE ID which identifies the UE.The UE ID may also be an application user ID of the UE. If UE B acceptsthe communication request from UE A, UE B transmits a directcommunication response message including its UE ID to UE A. UE A and UEB may know each other's UE ID as a part of a discovery message. UE A andUE B may periodically transmit discovery messages. The UE IDs of UEswith which the UE wants to communicate may be preconfigured in the UE.

Upon receipt of the direct communication request message from UE A, theeNB verifies the direct communication request message and then assignsTx UE pair ID 1 and Rx UE pair ID 2 to UE A. The eNB transmits theassigned Tx UE pair ID and Rx UE pair ID to UE A in a directcommunication response message in operation 3103. The eNB may transmitother parameters related to direct communication in the directcommunication response message. Upon receipt of the direct communicationrequest message from UE B, the eNB verifies the direct communicationrequest message and then assigns Tx UE pair ID 2 and Rx UE pair ID 1 toUE B. The eNB transmits the assigned Tx UE pair ID and Rx UE pair ID toUE B in a direct communication response message in operation 3104. TheeNB may transmit other parameters related to direct communication in thedirect communication response message.

Upon receipt of the direct communication response messages, UE and UE Btransmit direct communication complete messages to the eNB respectivelyin operations 3105 and 3106. UE A and UE B perform operations using theassigned Tx UE pair IDs and Rx UE pair IDs. UE A and UE B monitor aPDCCH or EPDCCH using the Tx UE pair IDs, Rx UE pair IDs, and a reservedC-RNTI in operations 3107 and 3108. This monitoring may be added tomonitoring a PDCCH or EPDCCH using C-RNTIs assigned to UE A and UE B forUE-eNB communication.

If UE A wants to transmit data to UE B on the D2D communication link, UEA transmits a D2D BSR to the eNB in operation 3111. The D2D BSR mayinclude the ID of UE B, UE pair ID 1, or UE pair ID 2. Upon receipt ofthe D2D BSR, the eNB transmits a grant in a PDCCH or EPDCCH masked withthe reserved C-RNTI and UE pair ID 1 in operations 3112 and 3113. ThePDCCH or EPDCCH may be received by both UE A and UE B. As UE pair ID 1corresponds to the Tx UE pair ID of UE A, UE A transmits data inallocated resources in operation 3114 and UE B receives data in theallocated resources in operation 3115.

If UE B wants to transmit data to UE A on the D2D communication link, UEB transmits a D2D BSR to the eNB in operation 3121. The D2D BSR mayinclude the ID of UE A, UE pair ID 1, or UE pair ID 2. Upon receipt ofthe D2D BSR, the eNB transmits a grant in a PDCCH or EPDCCH masked withthe reserved C-RNTI and UE pair ID 2 in operations 3122 and 3123. ThePDCCH or EPDCCH may be received by both UE A and UE B. As UE pair ID 2corresponds to the Tx UE pair ID of UE B, UE B transmits data inallocated resources in operation 3124 and UE A receives data in theallocated resources in operation 3125.

While UL subframes are used for direct communication in the foregoingdescription and drawings, the present disclosure is equally applicablefor the cases in which DL subframes or both DL and UL subframes are usedfor direct communication. The present disclosure is also applicable to asystem operating in FDD mode or TDD mode.

In an embodiment in which two UE pair IDs are assigned to a UE pair, onemay be semi-persistently scheduled and the other may be normallyscheduled. In another embodiment in which a UE pair is assigned one UEpair ID, it may be semi-persistently scheduled or normally scheduled.

Embodiment 5

A fourth embodiment of the present disclosure provides a method foridentifying Tx resources and Rx resources using a unified C-RNTI (sameC-RNTI for D2D communication and communication with eNB). In thisembodiment resource information is indicated to both UEs of UE pairusing single control channel transmission by eNB. In this embodiment itis assumed that both UEs of UE pair is connected with same eNB.

In the fourth embodiment of the present disclosure, it is assumed thatselective subframes (DL or UL or both) are signaled or reserved for onlydirect communication. A UE(s) does not use these selected subframes tocommunicate with an eNB. The granularity of reservation for directcommunication may be frames, slots, or symbols. An eNB assigns oneunified C-RNTI to a UE for all types of communications (for example,communication between a UE and an eNB, communication between a UE andone or more other UEs, and communication between a UE and an eNB and oneor more other UEs). A C-RNTI is assigned to the UE when it establishes aconnection with the eNB or with another UE. If the UE already has aconnection either with the eNB or the other UE, then a new C-RNTI is notassigned during subsequent connection establishment with the UE or theeNB. The assigned unified C-RNTI is released only when the UE has noconnection with any other UE and the eNB. Even if the unified C-RNTI isestablished during connection setup with the eNB, it is not releasedduring the connection release with the eNB if the UE has a directconnection with at least one other UE. If the C-RNTI established duringthe connection setup with the eNB is released during the connectionrelease with the eNB and if the UE has a direct connection with at leastone other UE, a new C-RNTI is assigned to the UE. The unified C-RNTI maybe a temporary C-RNTI, a semi-persistently scheduled C-RNTI, or aC-RNTI.

FIG. 32 illustrates a method for using a unified C-RNTI for directioncommunication according to an embodiment of the present disclosure.

Referring to FIG. 32, C-RNTI 1 and C-RNTI 2 are assigned to UE1 and UE2,respectively for communication with an eNB. UE1 and UE2 use the assignedC-RNTIs (i.e. C-RNTI 1 and C-RNTI 2) to receive and decode a PDCCH inthe DL subframes, DL SF n and DL SF n+1 to receive resources fortransmitting data in the UL subframes, UL SF n+2 and UL SF n+3,respectively. UE1 and UE2 also use the assigned C-RNTIs (i.e. C-RNTI 1and C-RNTI 2) to receive and decode a PDCCH in the DL subframes, DL SF nand DL SF n+1 to receive resources for receiving DL packets in the DLsubframes, DL SF n and DL SF n+1 respectively. The same C-RNTI (i.e.C-RNTI 1) as assigned to UE1 is assigned to UE pair x. The UEs of UEpair x use C-RNTI 1 in the DL subframe, DL SF n+2 to receive resourcesfor direct communication in the UL subframe, UL SF n+4. UE1 does not useC-RNTI 1 in the DL subframe, DL SF n+2 to receive resources fortransmitting data in the UL subframe, UL SF n+4. However, UE1 may useC-RNTI 1 in the DL subframe, DL SF n+2 to receive resources forreceiving DL packets in the DL subframe, DL SF n+3.

A method for resource allocation signaling and identifying atransmitting UE and a receiving UE of UE Pair will be described below.

An eNB allocates resources for direct communication between a UE pair. Acontrol region (that is, a PDCCH) indicates resources for directcommunication as well as resources for communication with the eNB. Theresources for direct communication are indicated to the UEs of the UEpair using a single transmission. In an embodiment of the presentdisclosure, a C-RNTI of a transmitting UE amongst the UEs of the UE pairis used in a PDCCH to indicate resources for direct communication. Thetransmitting and receiving UEs of the UE pair receive and decode thePDCCH using the C-RNTI of the transmitting UE. The UEs of the UE pairexchange each other's C-RNTI during connection setup either directly orvia the network.

The transmitting UE may participate in direct communication with aplurality of UEs. For example, a transmitting UE, UE1 may be connectedto UE2 and UE3. If the C-RNTI of UE1 is used to indicate the resources,then a method is needed to determine whether the allocated resourceswill be used by UE1 to transmit data to UE2 or UE3. A method is alsoneeded to determine whether UE2 or UE3 should receive the indicatedresources using the C-RNTI of UE1. For this purpose, the eNB assigns aTx/Rx index (Tx-Rx-Idx) to each UE performing the Tx role in directcommunication. The Tx/Rx index is independently maintained for each UEperforming the Tx role. The Tx/Rx index of a UE distinguishes aplurality of connections of the UE with other UEs. For example, if UE1is connected to UE2 and UE3 and transmits data to both UE2 and UE3, theTx/Rx index of UE1 for a UE1-UE2 connection may be 0 whereas the Tx/Rxindex of UE1 for a UE1-UE3 connection may be 1. A Tx/Rx index isassigned at the time of connection establishment between the UEs of a UEpair. A Tx/Rx index is assigned to each UE of a UE pair.

FIG. 33 illustrates an example of using a unified C-RNTI and a Tx/Rxindex for direct communication according to an embodiment of the presentdisclosure.

Referring to FIG. 33, for a pair of UEp and UEq, the Tx/Rx indexes ofboth UEp and UEq are 0 because UEp and UEq are not connected to anyother UE. For a pair of UEa and UEc, the Tx/Rx indexes of both UEa andUEc are 0 because UEc is not connected to any other UE and for UEa, theconnection with UEc is the first connection. For a pair of UEa and UEb,the Tx/Rx index of UEa is 1 and the Tx/Rx index of UEb is 0. UEb is notconnected to any other UE and hence its Tx/Rx index is 0. UEa hasconnections with UEb and UEc and hence its Tx/Rx index for theconnection with UEb is 1.

FIG. 34 is a diagram illustrating a signal flow for allocating a Tx/Rxindex in allocating resources for D2D communication within a cellaccording to an embodiment of the present disclosure.

Referring to FIG. 34, UE A initiates direct communication establishmentwith UE B and transmits a direct communication request message includingits UE ID to UE B in operation 3401. According to an embodiment, the UEID may be an ID assigned to UE A for ProSe communication (that is, aProSe UE ID). Or the UE ID may be an idle mode ID assigned to UE A (thatis, an S-TMSI). Or the UE ID may be a GUTI assigned to UE A. If UE Baccepts the direct communication request from UE A, UE B transmits adirect communication response message including its UE ID to UE A, inoperation 3403. UE A and UE B transmit direct communication requestmessages to an eNB respectively in operations 3405 and 3407. Each of UEA and UE B includes the UE IDs of the UE B and UE A in its directcommunication request message. The order of operations 3405 and 3407 maybe changed.

Upon receipt of the direct communication request message from UE A, theeNB verifies the direct connection request message, assigns Tx/Rxindexes to UE A and UE B, and transmits the assigned Tx/Rx indexes andthe C-RNTI of UE B to UE A in a direct communication response message inoperation 3409. The C-RNTI of UE B may be included only if the C-RNTI isnewly assigned to UE B. If a C-RNTI has not been assigned to UE B yet,eNB1 assigns the C-RNTI to UE B. The eNB may transmit other parametersrelated to direct communication in the direct communication responsemessage to UE A. Upon receipt of the direct communication responsemessage from the eNB, UE A transmits a direct communication completemessage to the eNB in operation 3413.

Likewise, upon receipt of the direct communication request message fromUE B, the eNB verifies the direct connection request message, assignsthe Tx/Rx indexes to UE A and UE B, and transmits the assigned Tx/Rxindexes and the C-RNTI of UE A to UE B in a direct communicationresponse message in operation 3411. The C-RNTI of UE A may be includedonly if the C-RNTI is newly assigned to UE A. If a C-RNTI has not beenassigned to UE A yet, the eNB assigns the C-RNTI to UE A. The eNB maytransmit other parameters related to direct communication in the directcommunication response message to UE B. Upon receipt of the directcommunication response message from the eNB, UE B transmits a directcommunication complete message to the eNB in operation 3415.Subsequently, UE A and UE B perform D2D communication using the assignedTx/Rx indexes and C-RNTIs.

The C-RNTIs may be exchanged between UE A and UE B during directcommunication request and response signaling between UE A and UE B.

FIG. 35 is a diagram illustrating a signal flow for allocating Tx-Rxindexes to UEs according to an embodiment of the present disclosure.

Referring to FIG. 35, five connections are sequentially establishedamong UE A, UE B, UE C and UE D in operations 3501 to 3509. The firstconnection for bidirectional communication is established between UE Aand UE B in operation 3501. This connection is the first connectionbetween UE A and UE B for which they perform a Tx role and hence each ofthem is assigned Tx_Rx_Idx 0. The second connection for bidirectionalcommunication is established between UE B and UE C in operation 3503. UEB performs a Tx role for the earlier connection with UE A and a newconnection with UE C. So UE B is assigned Tx_Rx_Idx 1 for the connectionwith UE C. For UE C, the connection with UE B is the first connectionand hence it is assigned Tx_Rx_Idx 0. The third connection forbidirectional communication is established between UE C and UE D inoperation 3505. UE C performs a Tx role for the earlier connection withUE B and a new connection with UE D. So UE C is assigned Tx_Rx_Idx 1 forthe connection with UE D. For UE D, the connection with UE C is thefirst connection and hence it is assigned Tx_Rx_Idx 0. The fourthconnection for bidirectional communication is established between UE Band UE D in operation 3507. UE B performs a Tx role for the earlierconnections with UE A and UE B and a new connection with UE D. So UE Bis assigned Tx_Rx_Idx 2 for the connection with UE D. UE D performs a Txrole for the earlier connection with UE C and a new connection with UEB. So UE D is assigned Tx_Rx_Idx 1 for the connection with UE B. Thefifth connection for bidirectional communication is established betweenUE A and UE C in operation 3509. UE C performs a Tx role for the earlierconnection with UE D and UE B and a new connection with UE A. So UE C isassigned Tx_Rx_Idx 2 for the connection with UE A. UE A performs a Txrole for the earlier connection with UE B and a new connection with UEC. So UE A is assigned Tx_Rx_Idx 1 for the connection with UE C.

A UE may maintain a Tx/Rx index. That is, the UE assigns a Tx/Rx indexfor its connection with another UE and transmits information about theassigned Tx/Rx index to an eNB during direct connection setup. The eNBstores this information. The UE may transmit the Tx/Rx index in a directcommunication request message to the eNB. The eNB transmits the Tx/Rxindex of a UE to which the UE is connected in a direct communicationresponse message. Alternatively, the UE transmits its Tx/Rx index for anew connection in a direct communication request message to the eNB.Each UE of a UE pair also exchanges Tx/Rx indexes directly with theother UE through a direct link. The property of a Tx/Rx index is thesame irrespective of whether it is assigned by an eNB or a UE. If theeNB assigns a Tx/Rx index, the eNB should maintain information aboutTx/Rx indexes assigned to all UEs. If the UE assigns a Tx/Rx index, theUE should maintain information about the Tx/Rx index, thereby reducingthe load of the eNB.

A method for monitoring a DL frequency using a unified C-RNTI, forresource allocation will be described.

If a UE is connected to an eNB only, the UE decodes a PDCCH using anassigned C-RNTI to determine resources for transmitting and receivingdata in DL and UL subframes. If a UE is connected to one or more otherUEs, a transmitting UE decodes a PDCCH using its C-RNTI to determineresources during time durations (for example, UL subframes) meant fordirect communication. If this transmitting UE is connected to aplurality of UEs, for transmission, the UE uses a Tx/Rx index inaddition to the C-RNTI to determine a UE to which it has to transmitdata. The receiving UE decodes a PDCCH using the C-RNTI of another UE towhich it is connected and a Tx/Rx index assigned to the other(transmitting) UE for this connection during time durations (forexample, UL subframes) meant for direct communication. If the receivingUE is connected to a plurality of UEs, for reception, the same operationis repeated.

FIG. 36 illustrates an example of distinguishing resources for UE paircommunication from resources of other UEs within the coverage area of aneNB according to an embodiment of the present disclosure.

Referring to FIG. 36, UE1 and UE2 are engaged in direct communication.UE1 transmits data and UE2 receives the data. C-RNTI 1 is assigned toUE1 and C-RNTI 2 is assigned to UE2. Because UE1 and UE2 are notconnected to any other UE, the Tx/Rx index of UE1 is 0 and the Tx/Rxindex of UE2 is 0. UE1 and UE2 receive and decode a PDCCH using C-RNTI1and the Tx/Rx index (=0) of UE1.

FIG. 37 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for communication betweena UE of the UE pair and an eNB according to an embodiment of the presentdisclosure.

Referring to FIG. 37, UE1 and UE2 are engaged in direct communication.C-RNTI 1 and C-RNTI 2 are assigned to UE1 and UE2, respectively. UE1transmits data and UE2 receives the data. Also, UE2 transmits data andUE1 receives the data. UE1 and UE2 are not connected to any other UE.Therefore, for the connection between UE1 and UE2, the Tx/Rx index ofUE1 is 0 and the Tx/Rx index of UE2 is 0. UE1 and UE2 receive and decodea PDCCH using C-RNTI 1, C-RNTI 2, the Tx/Rx index (=0) of UE1, and theTx/Rx index (=0) of UE2. Specifically, UE1 searches for a PDCCH usingC-RNTI 1 and the Tx/Rx index of UE1 for Tx resources, and using C-RNTI 2and the Tx/Rx index of UE2 for Rx resources. Also, UE2 searches for aPDCCH using C-RNTI 2 and the Tx/Rx index of UE2 for Tx resources andusing C-RNTI 1 and the Tx/Rx index of UE1 for Rx resources.

FIG. 38 illustrates an example of distinguishing resources forcommunication between one UE pair from resources for communicationbetween another UE pair according to an embodiment of the presentdisclosure.

Referring to FIG. 38, UE1 and UE2 are engaged in direct communication,whereas UE1 and UE3 are engaged in direct communication. C-RNTI 1,C-RNTI 2, and C-RNTI 3 are assigned to UE1, UE2, and UE3, respectively.UE1 transmits data and UE2 receives the data. Also, UE1 transmits dataand UE3 receives the data. For the UE1-UE2 connection, the Tx/Rx indexof UE1 is 0 and the Tx/Rx index of UE2 is 0. For the UE1-UE3 connection,the Tx/Rx index of UE1 is 1 and the Tx/Rx index of UE3 is 0. UE1receives and decodes a PDCCH using C-RNTI 1 and the Tx/Rx indexes (=0and 1) of UE1. UE2 receives and decodes a PDCCH using C-RNTI 1 and theTx/Rx index (=zero) of UE1. UE3 receives and decodes a PDCCH usingC-RNTI 1 and the Tx/Rx index (=1) of UE1.

UE1 searches for a PDCCH using C-RNTI 1 and the Tx/Rx index (=0) of UE1for Tx resources for transmitting to UE2 and UE3. UE2 searches for aPDCCH using C-RNTI 1 and the Tx/Rx index (=0) of UE1 for Rx resourcesfor receiving from UE1. UE3 searches for a PDCCH using C-RNTI 1 and theTx/Rx index (=0) of UE1 for Rx resources for receiving from UE1.

Another method for identifying and signaling a transmitting/receiving UEpair will be described.

An eNB allocates resources for direct communication between a UE pair ina DL frequency. A control region (that is, a PDCCH) in the DL frequencyindicates resources for direct communication as well as resources forcommunication with the eNB. The resources for direct communication areindicated to the UEs of the UE pair using a single transmission. In anembodiment of the present disclosure, the C-RNTI of a receiving UEamongst the UEs of the UE pair is used in a PDCCH or a control region toindicate resources for direct communication. The transmitting andreceiving UEs of the UE pair receive and decode the PDCCH using theC-RNTI of the receiving UE. The UEs of the UE pair exchange theirC-RNTIs with each other during connection establishment either directlyor via the network.

A receiving UE may be involved in direct communication with a pluralityof UEs. For example, if a receiving UE, UE1 is connected to UE2 and UE3,the C-RNTI of UE1 is used to indicate resources for directcommunication. Accordingly, UE1 needs to determine whether to use theallocated resources to receive data from UE2 or UE3. Also, UE1 needs todetermine whether UE2 or UE3 should transmit data in the indicatedresources using the C-RNTI of UE1. For this purpose, the eNB assigns aTx/Rx index to each UE performing the Rx role in direct communication.The Tx/Rx index is independently maintained for each UE performing theRx role. The Tx/Rx index of a UE distinguishes a plurality ofconnections of the UE with other UEs. For example, if UE1 is connectedto UE2 and UE3 and receives data from both UE2 and UE3, the Tx/Rx indexof UE1 for the UE1-UE2 connection may be 0 whereas the Tx/Rx index ofUE1 for the UE1-UE3 connection may be 1. A Tx/Rx index is assigned atthe time of connection establishment between the UEs of the UE pair. ATx/Rx index is assigned to each UE of the UE Pair.

FIG. 39 illustrates a method for using a unified C-RNTI and a Tx/Rxindex for direct communication according to an embodiment of the presentdisclosure.

Referring to FIG. 39, a unified C-RNTI is assigned to every UE engagedin communication according to an embodiment of the present disclosure.For a pair of UEp and UEq, both Tx/Rx indexes of UEp and UEq are 0because UEp and UEq are not connected to any other UE. For a pair of UEaand UEb, both Tx/Rx indexes of UEa and UEb are 0 because UEb is notconnected to any other UE and for UEa the connection with UEb is thefirst connection. For a pair of UEa and UEc, the Tx/Rx index of UEa is 1and the Tx/Rx index of UEc is 0. UEc is not connected to any other UEand hence its Tx/Rx index is 0. UEa is connected to UEb and UEc andhence its Tx/Rx index for the connection with UEc is 1.

FIG. 40 illustrates an example of distinguishing resources forcommunication between a UE pair from other resources within the coveragearea of an eNB according to an embodiment of the present disclosure.

Referring to FIG. 40, UE1 and UE2 are engaged in direct communication.UE1 transmits data and UE2 receives the data. C-RNTI 1 is assigned toUE1 and C-RNTI 2 is assigned to UE2. Because UE1 and UE2 are notconnected to any other UE, the Tx/Rx index of UE1 is 0 and the Tx/Rxindex of UE2 is 0. UE1 and UE2 receive and decode a PDCCH using C-RNTI 2and the Tx/Rx index (=0) of the receiving UE, UE2.

FIG. 41 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for communication betweenan eNB and a UE of the UE pair according to an embodiment of the presentdisclosure.

Referring to FIG. 41, UE1 and UE2 are engaged in direct communication.C-RNTI 1 and C-RNTI 2 are assigned to UE1 and UE2, respectively. UE1transmits data and UE2 receives the data. Also, UE2 transmits data andUE1 receives the data. UE1 and UE2 are not connected to any other UE.Therefore, for the connection between UE1 and UE2, the Tx/Rx index ofUE1 is 0 and the Tx/Rx index of UE2 is 0. UE1 and UE2 receive and decodea PDCCH using C-RNTI 1, C-RNTI 2, the Tx/Rx index (=0) of UE1, and theTx/Rx index (=0) of UE2. Specifically, UE1 searches for a PDCCH usingC-RNTI 2 and the Tx/Rx index of UE2 for Tx resources, and using C-RNTI-1and the Tx/Rx index of UE1 for Rx resources. Also, UE2 searches for aPDCCH using C-RNTI 1 and the Tx/Rx index of UE1 for Tx resources andusing C-RNTI 2 and the Tx/Rx index of UE2 for Rx resources.

FIG. 42 illustrates an example of distinguishing resources forcommunication between one UE pair from resources for communicationbetween another UE pair according to an embodiment of the presentdisclosure.

Referring to FIG. 42, UE1 and UE2 are engaged in direct communication,and UE1 and UE3 are engaged in direct communication. C-RNTI 1, C-RNTI 2,and C-RNTI 3 are assigned to UE1, UE2, and UE3, respectively. UE1receives data and UE2 transmits data. Also UE1 receives data and UE3transmits data. For the UE1-UE2 connection, the Tx/Rx index of UE1 is 0and the Tx/Rx index of UE2 is 0. For the UE1-UE3 connection, the Tx/Rxindex of UE1 is 1 and the Tx/Rx index of UE3 is 0. UE1 receives anddecodes a PDCCH using C-RNTI 1 and the Tx/Rx indexes (=0 and 1) of UE1.UE2 receives and decodes a PDCCH using C-RNTI 1 and the Tx/Rx index (=0)of UE1. UE3 receives and decodes a PDCCH using C-RNTI 1 and the Tx/Rxindex (=1) of UE1.

UE1 searches for a PDCCH using C-RNTI 1 and the Tx/Rx index (=0) of UE1for Rx resources for receiving from UE2. UE1 searches for a PDCCH usingC-RNTI 1 and Tx-Rx-Idx (=0) of UE1 for Rx resources for receiving datafrom UE3. UE2 searches for a PDCCH using C-RNTI 1 and the Tx/Rx index(=0) of UE1 for Tx resources for transmitting data to UE1. UE3 searchesfor a PDCCH using C-RNTI 1 and the Tx/Rx index (=0) of UE1 for Txresources for transmitting data to UE1.

A third method for identifying and signaling a transmitting/receiving UEpair will be described.

An eNB allocates resources for direct communication between a UE pair ina DL frequency. A control region of the DL frequency indicates theresources for direct communication between the UE pair as well asresources for communication with the eNB. The resources for directcommunication are indicated to the UEs of the UE pair by a singletransmission. A C-RNTI of a transmitting UE is used to mask a CRC of aPDCCH and a C-RNTI of receiving UE is added inside the contents of thePDCCH. The UEs of the UE pair exchange each other's C-RNTI duringconnection establishment either directly or via the network. A UE havingdirect communication with another UE monitors the DL frequency forresource allocation using a unified C-RNTI. If the UE is connected tothe eNB only, the UE uses the assigned C-RNTI to decode the PDCCH fordetermining resources for receiving and transmitting data in DL and ULsubframes. If the UE is connected to one or more other UEs, the UE usesthe assigned C-RNTI and the C-RNTIs of other UEs with which it iscommunicating to decode the PDCCH for determining resources forreceiving and transmitting data in DL and UL subframes.

A transmitting UE and a receiving UE are identified as follows.

A transmitting UE decodes a PDCCH using its C-RNTI to determineresources for time durations (for example, UL subframes) meant fordirect communication with other UEs. If the PDCCH is decoded using theC-RNTI of the UE and the C-RNTI of another UE with which the UE iscommunicating is present in the decoded PDCCH, the UE uses the resourcesfor transmission. The UE transmits data to a UE whose C-RNTI is presentin the decoded PDCCH. If the C-RNTI in the decoded PDCCH does not belongto a UE with which it is communicating, it ignores the decoded PDCCH.

A receiving UE decodes a PDCCH using the C-RNTI of another UE connectedto the receiving UE to determine resources for time durations (forexample, UL subframes) meant for direct communication with the other UE.If the PDCCH is decoded using the C-RNTI of the UE communicating withthe receiving UE and the C-RNTI of the receiving UE is present in thedecoded PDCCH, the UE uses the resources for reception. The UE receivesdata from the UE whose C-RNTI is used to decode the PDCCH. If the C-RNTIin the decoded PDCCH does not belong to the UE, the UE ignores thedecoded PDCCH.

FIG. 43 illustrates an operation for allocating and exchanging a unifiedC-RNTI according to an embodiment of the present disclosure.

Referring to FIG. 43, UE A initiates direct communication establishmentwith UE B and transmits a direct communication request message includingits UE ID to UE B in operation 4301. According to an embodiment, the UEID may be an ID assigned to UE A for ProSe communication (that is, aProSe UE ID). Or the UE ID may be an idle mode ID assigned to UE A (thatis, an S-TMSI). Or the UE ID may be a GUTI assigned to UE A. If UE Baccepts the direct communication request from UE A, UE B transmits adirect communication response message including its UE ID to UE A, inoperation 4303. UE A and UE B transmit direct communication requestmessages to an eNB respectively in operations 4305 and 4307. Each of UEA and UE B includes the UE IDs of the UE B and UE A in its directcommunication request message. The order of operations 4305 and 4307 maybe changed.

Upon receipt of the direct communication request message from UE A, theeNB verifies the direct connection request message and transmits theC-RNTI of UE B to UE A in a direct communication response message inoperation 4309. The C-RNTI of UE B may be included only if the C-RNTI isnewly assigned to UE B. If a C-RNTI has not been assigned to UE B yet,eNB1 assigns the C-RNTI to UE B. The eNB may transmit other parametersrelated to direct communication in the direct communication responsemessage to UE A. Upon receipt of the direct communication responsemessage from the eNB, UE A transmits a direct communication completemessage to the eNB in operation 4313.

Likewise, upon receipt of the direct communication request message fromUE B, the eNB verifies the direct connection request message andtransmits the C-RNTI of UE A to UE B in a direct communication responsemessage in operation 4311. The C-RNTI of UE A may be included only ifthe C-RNTI is newly assigned to UE A. If a C-RNTI has not been assignedto UE A yet, the eNB assigns the C-RNTI to UE A. The eNB may transmitother parameters related to direct communication in the directcommunication response message to UE B. Upon receipt of the directcommunication response message from the eNB, UE B transmits a directcommunication complete message to the eNB in operation 4315.Subsequently, UE A and UE B perform D2D communication. The C-RNTIs maybe exchanged between UE A and UE B during direct communication requestand response signaling between UE A and UE B.

FIG. 44 illustrates an example of distinguishing resources for UE paircommunication from other resources within the coverage area of an eNBaccording to an embodiment of the present disclosure.

Referring to FIG. 44, UE1 and UE2 are engaged in direct communication.UE1 transmits data and UE2 receives the data. C-RNTI 1 is assigned toUE1 and C-RNTI 2 is assigned to UE2. UE1 and UE2 are not connected toany other UE. UE1 and UE2 receive and decode a PDCCH using C-RNTI 1 of atransmitting UE, UE1. If C-RNTI 2 is included in a decoded PDCCH, UE1transmits data in indicated resources and UE2 receives data in theindicated resources.

FIG. 45 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for communication betweenan eNB and a UE of the UE pair according to an embodiment of the presentdisclosure.

Referring to FIG. 45, UE1 and UE2 are engaged in direct communication.C-RNTI 1 and C-RNTI 2 are assigned to UE1 and UE2, respectively. UE1transmits data and UE2 receives the data. Also, UE2 transmits data andUE1 receives the data. UE1 and UE2 are not connected to any other UE.UE1 and UE2 receive and decode a PDCCH using C-RNTI 1 and C-RNTI 2. Ifresources are indicated by a PDCCH masked with C-RNTI 1 and C-RNTI 2 isincluded in the PDCCH, UE1 transmits data and UE 2 receives data. Ifresources are indicated by a PDCCH masked with C-RNTI 2 and C-RNTI 1 isincluded in the PDCCH, UE2 transmits data and UE1 receives data.

FIG. 46 illustrates an example of distinguishing resources forcommunication between one UE pair from resources for communicationbetween another UE pair according to an embodiment of the presentdisclosure.

Referring to FIG. 46, UE1 and UE2 are engaged in direct communication,and UE1 and UE3 are engaged in direct communication. C-RNTI 1, C-RNTI 2,and C-RNTI 3 are assigned to UE1, UE2, and UE3, respectively. UE1receives data and UE2 transmits data. Also UE1 receives data and UE3transmits data. UE2 searches for a PDCCH using C-RNTI 2 and UE3 searchesfor a PDCCH using C-RNTI 3. If resources are indicated by a PDCCH maskedwith C-RNTI 2 and C-RNTI 1 is included in the PDCCH, UE2 transmits dataand UE 1 receives data. If resources are indicated by a PDCCH maskedwith C-RNTI 3 and C-RNTI 1 is included in the PDCCH, UE3 transmits dataand UE1 receives data.

A fourth method for identifying and signaling a transmitting/receivingUE pair will be described.

An eNB allocates resources for direct communication between a UE pair ina DL frequency. A control region of the DL frequency indicates theresources for direct communication between the UE pair as well asresources for communication with the eNB. The resources for directcommunication are indicated to the UEs of the UE pair by a singletransmission. A C-RNTI of a receiving UE is used to mask a CRC of aPDCCH and a C-RNTI of a transmitting UE is added inside the contents ofthe PDCCH. The UEs of the UE pair exchange each other's C-RNTI duringconnection establishment either directly or via the network. A UE havingdirect communication with another UE monitors the DL frequency forresource allocation using a unified C-RNTI. If the UE is connected tothe eNB only, the UE uses the assigned C-RNTI to decode the PDCCH fordetermining resources for receiving and transmitting data in DL and ULsubframes. If the UE is connected to one or more other UEs, the UE usesthe assigned C-RNTI and the C-RNTIs of other UEs with which it iscommunicating to decode the PDCCH for determining resources forreceiving and transmitting data in DL and UL subframes.

A transmitting UE and a receiving UE are identified as follows.

A receiving UE decodes a PDCCH using its C-RNTI to determine resourcesfor time durations (for example, UL subframes) meant for directcommunication with other UEs. If the PDCCH is decoded using the C-RNTIof the UE and the C-RNTI of another UE with which the UE iscommunicating is present in the decoded PDCCH, the UE uses the resourcesfor reception. The UE receives data from a UE whose C-RNTI is present inthe decoded PDCCH. If the C-RNTI in the decoded PDCCH does not belong toa UE with which it is communicating, it ignores the decoded PDCCH.

A transmitting UE decodes a PDCCH using the C-RNTI of another UEconnected to the UE to determine resources for time durations (forexample, UL subframes) meant for direct communication with the other UE.If the PDCCH is decoded using the C-RNTI of the UE communicating withthe transmitting UE and the C-RNTI of the transmitting UE is present inthe decoded PDCCH, the UE uses the resources for transmission. The UEtransmits data to the UE whose C-RNTI is used to decode the PDCCH. Ifthe C-RNTI in the decoded PDCCH does not belong to the UE, the UEignores the decoded PDCCH.

FIG. 47 illustrates an example of distinguishing resources for UE paircommunication from other resources within the coverage area of an eNBaccording to an embodiment of the present disclosure.

Referring to FIG. 47, UE1 and UE2 are engaged in direct communication.UE1 transmits data and UE2 receives the data. C-RNTI 1 is assigned toUE1 and C-RNTI 2 is assigned to UE2. UE1 and UE2 are not connected toany other UE. UE1 and UE2 search for a PDCCH using C-RNTI 1 of areceiving UE, UE1. If C-RNTI 1 is included in a decoded PDCCH, UE1transmits data in indicated resources and UE2 receives data in theindicated resources.

FIG. 48 illustrates an example of distinguishing resources forcommunication between a UE pair from resources for communication betweenan eNB and a UE of the UE pair according to an embodiment of the presentdisclosure.

Referring to FIG. 48, UE1 and UE2 are engaged in direct communication.C-RNTI 1 and C-RNTI 2 are assigned to UE1 and UE2, respectively. UE1transmits data and UE2 receives the data. Also, UE2 transmits data andUE1 receives the data. UE1 and UE2 are not connected to any other UE.UE1 and UE2 search for a PDCCH using C-RNTI 1 and C-RNTI 2. If resourcesare indicated by a PDCCH masked with C-RNTI 1 and C-RNTI 2 is includedin the PDCCH, UE2 transmits data and UE1 receives data. If resources areindicated by a PDCCH masked with C-RNTI 2 and C-RNTI 1 is included inthe PDCCH, UE1 transmits data and UE2 receives data.

FIG. 49 illustrates an example of distinguishing resources forcommunication between one UE pair from resources for communicationbetween another UE pair according to an embodiment of the presentdisclosure.

Referring to FIG. 49, UE1 and UE2 are engaged in direct communication,and UE1 and UE3 are engaged in direct communication. C-RNTI 1, C-RNTI 2,and C-RNTI 3 are assigned to UE1, UE2, and UE3, respectively. UE1receives data and UE2 transmits data. Also UE1 receives data and UE3transmits data. UE1, UE2, and UE3 search for a PDCCH using C-RNTI 1. Ifresources are indicated by a PDCCH masked with C-RNTI 1 and C-RNTI 2 isincluded in the PDCCH, UE2 transmits data and UE1 receives data. Ifresources are indicated by a PDCCH masked with C-RNTI 1 and C-RNTI 3 isincluded in the PDCCH, UE3 transmits data and UE1 receives data.

A fifth method for identifying and signaling a transmitting/receiving UEpair will be described.

An eNB allocates resources for direct communication between a UE pair ina DL frequency. A control region of the DL frequency indicates theresources for direct communication between the UE pair as well asresources for communication with the eNB. The resources for directcommunication are indicated to the UEs of the UE pair by a singletransmission. A C-RNTI of a transmitting UE is used to indicate theresources for direct communication in a PDCCH or a control region.Transmitting and receiving UEs of a UE pair receive and decode a PDCCHusing the C-RNTI of the transmitting UE. The UEs of the UE pair exchangeeach other's C-RNTI during connection establishment either directly orvia the network.

A transmitting UE may participate in direct communication with aplurality of UEs. For example, if UE1 being a transmitting UE isconnected to UE2 and UE3, the C-RNTI of UE1 is used to indicateresources for direct communication. Therefore, UE1 needs to determine towhich UE between UE2 and UE3 it should transmit data. Also, UE1 needs todetermine which UE should receive data using the indicated resourcesusing the C-RNTI of UE1. For this purpose, an eNB assigns a UE pair IDto each UE playing a Tx role in direct communication in an embodiment ofthe present disclosure. A UE pair ID distinguishes a plurality ofconnections between UEs. The eNB assigns a different UE pair ID to eachUE pair. In an embodiment, an MME may assign a UE pair ID in order toprevent update of the UE pair ID during a UE's movement between eNBs.

A UE pair ID is assigned in the same manner as illustrated in FIG. 34,except that the UE pair ID is assigned to UE A and UE B instead of Tx/Rxindexes.

A UE having direct communication with another UE monitors a DL frequencyfor resource allocation using a unified C-RNTI. Specifically, if the UEis connected to the eNB only, the UE uses the assigned C-RNTI to decodethe PDCCH for determining resources for receiving and transmitting datain DL and UL subframes. If the UE is connected to one or more other UEs,a transmitting UE uses its C-RNTI to decode a PDCCH for determining timedurations (for example, UL subframes) for direct communication. If thetransmitting UE is connected to a plurality of UEs, for transmission,the transmitting UE uses a UE pair ID in addition to a C-RNTI todetermine a UE to which the transmitting UE should transmit data. Areceiving UE decodes a PDCCH using the C-RNTI of another UE connected tothe receiving UE and a UE pair ID assigned to the connection in order todetermine resources for time durations (for example, UL subframes) fordirect communication. If the receiving UE is connected to a plurality ofUEs, for reception, the same operation is repeated.

If a control information format of a decoded PDCCH for communicationwith an eNB is different from a control information format for directcommunication, the first to fifth methods for identifying and signalinga Tx UE pair and an Rx UE pair may be used even when a dedicatedsubframe is not allocated for direct communication. Only if a UE canidentify the control information formats for communication with an eNBand direct communication after decoding a PDCCH, the first to fourthmethods for identifying and signaling a Tx UE pair and an Rx UE pair maybe used even when a dedicated subframe is not allocated for directcommunication.

DL control information delivered on a control channel (that is, a PDCCH)to indicate resources for communication with an eNB has a differentformat from DL control information delivered on a control channel (thatis, a PDCCH) to indicate resources for direct communication. The size ofDL control information delivered on a control channel to indicateresources for direct communication may be different from the size ofexisting DL control information, so that a UE may determine whether DLcontrol information indicates resources for direct communication, whenthe UE receives and decodes a control channel.

In another embodiment, different C-RNTIs may be assigned forcommunication with an eNB and communication with another UE. A UE may beassigned an additional C-RNTI to communicate with another UE through adirect communication link. If the UE communicates with one or more otherUEs through direct communication link, the UE is assigned one C-RNTI. Ifthe UE communicates with one or more other UEs through directcommunication links and also communicates with the eNB, the UE isassigned two C-RNTIs for a direct communication link and a link with theeNB. In this case, the additional C-RNTI assigned to the UE, for directcommunication may be used as a unified C-RNTI in the first to fifthmethods for identifying and signaling a Tx UE pair and an Rx UE pair.

FIG. 50 is a block diagram of an eNB according to an embodiment of thepresent disclosure.

Referring to FIG. 50, an eNB 5000 may include a transceiver 5010 forperforming data communication with various network nodes and a UE and acontroller 5020 for controlling the transceiver 5010. In the presentdisclosure, the foregoing operations of an eNB may be interpreted asperformed under control of the controller 5020.

While the transceiver 5010 and the controller 5020 are shown in FIG. 50as separately configured, the transceiver 5010 and the controller 5020may be incorporated into a single component.

FIG. 51 is a block diagram of a UE according to an embodiment of thepresent disclosure.

Referring to FIG. 51, a UE 5100 may include a transceiver 5110 forperforming data communication with various network nodes and an eNB anda controller 5120 for controlling the transceiver 5110. In the presentdisclosure, the foregoing operations of a UE may be interpreted asperformed under control of the controller 5120.

While the transceiver 5110 and the controller 5120 are shown in FIG. 51as separately configured, the transceiver 5110 and the controller 5120may be incorporated into a single component.

The proposed method and apparatus for performing D2D communication maybe implemented as computer-readable code in a computer-readablerecording medium. The computer-readable recording medium may include anykind of recording device storing computer-readable data. Examples of therecording medium may include Read Only Memory (ROM), Random AccessMemory (RAM), optical disk, magnetic tape, floppy disk, hard disk,non-volatile memory, and the like, and may also include the medium thatis implemented in the form of carrier waves (for example, transmissionover the Internet). In addition, the computer-readable recording mediummay be distributed over the computer systems connected over the network,and computer-readable codes may be stored and executed in a distributedmanner.

As is apparent from the foregoing description, upon accessing the Wi-Ficommunication network, the electronic device may receive a variety ofservice information from an operator or a venue providing the Wi-Ficommunication network, making it possible for the operator to provide avariety of service information to the users, contributing to theimprovement of the advertising efficiency.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method for performing Device-to-Device (D2D)communication, the method comprising: being assigned a transmission andreception indicator and an index during D2D connection setup between aUser Equipment (UE) and a Base Station (BS) by the UE, the transmissionand reception indicator indicating a transmission role or a receptionrole and the index indicating another UE for D2D communication;receiving the transmission and reception indicator, the index, andresource information for the D2D communication on a control channel bythe UE; and performing, by the UE, a transmission operation or areception operation to or from the other UE indicated by the index inresources indicated by the resource information according to thetransmission role or the reception role indicated by the transmissionand reception indicator.
 2. The method of claim 1, wherein a differentindex is assigned to each D2D connection.
 3. The method of claim 2,wherein the index is a pair of a transmission index and a receptionindex and one index pair is assigned to each D2D connection, and whereinthe index reception comprises receiving an index corresponding to thetransmission and reception indicator between the transmission index andthe reception index.
 4. The method of claim 1, wherein the beingassigned the transmission and reception indicator and the indexcomprises: transmitting a direct communication request message includingan IDentifier (ID) of the UE to the other UE and receiving a directcommunication response message including an ID of the other UE from theother UE by the UE; transmitting a direct communication request messageincluding the ID of the UE and the ID of the other UE to the BS by theUE; receiving a direct communication response message including anetwork temporary ID of the UE and the index from the BS by the UE; andtransmitting a direct communication complete message to the BS by theUE.
 5. The method of claim 1, wherein the being assigned thetransmission and reception indicator and the index comprises assigningan index indicating the UE and transmitting the assigned index to the BSby the UE.
 6. The method of claim 1, wherein, if the other UE isconnected to another BS different from the BS, the resources indicatedby the resource information are determined by coordination between theBS and the other BS.
 7. A method for performing Device-to-Device (D2D)communication, the method comprising: assigning a transmission andreception indicator and an index to a User Equipment (UE) during D2Dconnection setup between the UE and a Base Station (BS) by the BS, thetransmission and reception indicator indicating a transmission role or areception role and the index indicating another UE for D2Dcommunication; and transmitting the transmission and receptionindicator, the index, and resource information for the D2D communicationon a control channel to the UE by the BS, wherein the D2D communicationis performed between the UE and the other UE by performing atransmission operation or a reception operation between the UE and theother UE indicated by the index in resources indicated by the resourceinformation according to the transmission role or the reception roleindicated by the transmission and reception indicator.
 8. The method ofclaim 7, wherein a different index is assigned to each D2D connection.9. The method of claim 8, wherein the index is a pair of a transmissionindex and a reception index and one index pair is assigned to each D2Dconnection, and wherein the index transmission comprises transmitting anindex corresponding to the transmission and reception indicator betweenthe transmission index and the reception index.
 10. The method of claim7, wherein the assigning of the transmission and reception indicator andthe index to the UE comprises: receiving a direct communication requestmessage including an IDentifier (ID) of the UE and an ID of the other UEfrom the UE by the BS; transmitting a direct communication responsemessage including a network temporary ID of the UE and the index to theUE by the BS; and receiving a direct communication complete message fromthe UE by the BS.
 11. The method of claim 7, wherein the assigning ofthe transmission and reception indicator and the index to the UEcomprises receiving an index assigned by the UE from the UE by the BS.12. The method of claim 7, wherein, if the other UE is connected toanother BS different from the BS, the resources indicated by theresource information are determined by coordination between the BS andthe other BS.
 13. A User Equipment (UE) for performing Device-to-Device(D2D) communication, the UE comprising: a transceiver configured toperform D2D communication with another UE through a direct communicationlink; and a controller configured to control a transmission andreception indicator and an index to be assigned during D2D connectionsetup between the UE and a Base Station (BS), and to control thetransmission and reception indicator indicating a transmission role or areception role and the index indicating the other UE for the D2Dcommunication, reception of the transmission and reception indicator,the index, and resource information for the D2D communication on acontrol channel, and to perform of a transmission operation or areception operation to or from the other UE indicated by the index inresources indicated by the resource information according to thetransmission role or the reception role indicated by the transmissionand reception indicator.
 14. The UE of claim 13, wherein a differentindex is assigned to each D2D connection.
 15. The UE of claim 14,wherein the index is a pair of a transmission index and a receptionindex and one index pair is assigned to each D2D connection, and whereinthe controller controls reception of an index corresponding to thetransmission and reception indicator between the transmission index andthe reception index.
 16. The UE of claim 13, wherein the controllercontrols transmission of a direct communication request messageincluding an IDentifier (ID) of the UE to the other UE, reception of adirect communication response message including an ID of the other UEfrom the other UE, transmission of a direct communication requestmessage including the ID of the UE and the ID of the other UE to the BS,reception of a direct communication response message including a networktemporary ID of the UE and the index from the BS, and transmission of adirect communication complete message to the BS.
 17. The UE of claim 13,wherein the controller controls assignment of the index and transmissionof the assigned index to the BS.
 18. The UE of claim 13, wherein, if theother UE is connected to another BS different from the BS, the resourcesindicated by the resource information are determined by coordinationbetween the BS and the other BS.
 19. A Base Station (BS) for performingDevice-to-Device (D2D) communication, the BS comprising: a controllerconfigured to control assignment of a transmission and receptionindicator and an index to a User Equipment (UE) during D2D connectionsetup between the UE and the BS, the transmission and receptionindicator indicating a transmission role or a reception role and theindex indicating another UE for D2D communication, and transmission ofthe transmission and reception indicator, the index, and resourceinformation for the D2D communication on a control channel to the UE;and a transceiver configured to communicate with at least one UE undercontrol of the controller, wherein the D2D communication is performedbetween the UE and the other UE by performing a transmission operationor a reception operation between the UE and the other UE determined bythe index in resources indicated by the resource information accordingto the transmission role or the reception role indicated by thetransmission and reception indicator.
 20. The BS of claim 19, wherein adifferent index is assigned to each D2D connection.
 21. The BS of claim20, wherein the index is a pair of a transmission index and a receptionindex and one index pair is assigned to each D2D connection, and whereinthe controller controls transmission of an index corresponding to thetransmission and reception indicator between the transmission index andthe reception index.
 22. The BS of claim 19, wherein the controllercontrols reception of a direct communication request message includingan IDentifier (ID) of the UE and an ID of the other UE from the UE,transmission of a direct communication response message including anetwork temporary ID of the UE and the index to the UE, and reception ofa direct communication complete message from the UE.
 23. The BS of claim19, wherein the controller controls reception of an index assigned bythe UE from the UE.
 24. The BS of claim 19, wherein, if the other UE isconnected to another BS different from the BS, the resources indicatedby the resource information are determined by coordination between theBS and the other BS.
 25. A method for performing Device-to-Device (D2D)communication, the method comprising: being assigned a network temporaryIDentifier (ID) for D2D communication during D2D connection setup with aBase Station (BS) by a User Equipment (UE); receiving resourceinformation for the D2D communication on a control channel masked withthe network temporary ID by the UE; and performing a transmissionoperation or a reception operation to or from another UE determinedbased on the network temporary ID in resources indicated by the resourceinformation by the UE.
 26. The method of claim 25, wherein a differentnetwork temporary ID is assigned to each D2D connection, and wherein thebeing assigned of the network temporary ID comprises being assigned a UEindex for identifying UEs participating in the D2D communication, thecontrol channel includes the UE index, and the performing of atransmission operation or a reception operation comprises performing thetransmission operation or the reception operation according to a roledetermined based on the UE index.
 27. The method of claim 25, whereinthe network temporary ID is an ID pair of a transmission ID and areception ID that determine a role of the UE in each D2D connection,wherein the control channel is masked with one of the transmission IDand the reception ID included in the ID pair, and wherein the performingof a transmission operation or a reception operation comprisesperforming the transmission operation or the reception operationaccording to a role determined based on the transmission ID or thereception ID used for masking the control channel.
 28. A method forperforming Device-to-Device (D2D) communication, the method comprising:assigning a network temporary IDentifier (ID) for D2D communication to aUser Equipment (UE) during D2D connection setup with the UE by a BaseStation (BS); and transmitting resource information for the D2Dcommunication on a control channel masked with the network temporary IDto the UE by the BS, wherein the D2D communication is performed betweenthe UE and another UE by a transmission operation or a receptionoperation between the UE and the other UE determined based on thenetwork temporary ID in resources indicated by the resource information.29. The method of claim 28, wherein a different network temporary ID isassigned to each D2D connection, and wherein the assignment comprisesassigning a UE index for identifying UEs participating in the D2Dcommunication, the control channel includes the UE index, and the D2Dcommunication between the UE and the other UE is performed by thetransmission operation or the reception operation according to a roledetermined based on the UE index.
 30. The method of claim 28, whereinthe network temporary ID is an ID pair of a transmission ID and areception ID that determine a role of the UE in each D2D connection,wherein the control channel is masked with one of the transmission IDand the reception ID included in the ID pair, and wherein the D2Dcommunication is performed by the transmission operation or thereception operation according to a role determined based on thetransmission ID or the reception ID used for masking the controlchannel.
 31. A User Equipment (UE) for performing Device-to-Device (D2D)communication, the UE comprising: a transceiver configured to performD2D communication with another UE through a direct communication link;and a controller configured to control a network temporary IDentifier(ID) for D2D communication to be assigned during D2D connection setupwith a Base Station (BS), and to control reception of resourceinformation for the D2D communication on a control channel masked withthe network temporary ID and performing of a transmission operation or areception operation to or from another UE determined based on thenetwork temporary ID in resources indicated by the resource information.32. The UE of claim 31, wherein a different network temporary ID isassigned to each D2D connection, wherein the control channel includes aUE index for identifying UEs participating in the D2D communication,wherein the control channel includes the UE index, and wherein thecontroller controls a transmission operation or a reception operationaccording to a role determined based on the UE index.
 33. The UE ofclaim 31, wherein the network temporary ID is an ID pair of atransmission ID and a reception ID that determine a role of the UE ineach D2D connection, wherein the control channel is masked with one ofthe transmission ID and the reception ID included in the ID pair, andwherein the controller controls a transmission operation or a receptionoperation according to a role determined based on the transmission ID orthe reception ID used for masking the control channel.
 34. A BaseStation (BS) for performing Device-to-Device (D2D) communication, the BScomprising: a controller configured to control assignment of a networktemporary IDentifier (ID) for D2D communication to a User Equipment (UE)during D2D connection setup with the UE and transmission of resourceinformation for the D2D communication on a control channel masked withthe network temporary ID to the UE; and a transceiver configured tocommunicate with at least one UE under control of the controller,wherein the D2D communication is performed between the UE and another UEby a transmission operation or a reception operation between the UE andthe other UE determined based on the network temporary ID in resourcesindicated by the resource information.
 35. The BS of claim 34, wherein adifferent network temporary ID is assigned to each D2D connection, andwherein the controller controls assignment of a UE index for identifyingUEs participating in the D2D communication, the control channel includesthe UE index, and the D2D communication between the UE and the other UEis performed by the transmission operation or the reception operationaccording to a role determined based on the UE index.
 36. The BS ofclaim 34, wherein the network temporary ID is an ID pair of atransmission ID and a reception ID that determine a role of the UE ineach D2D connection, the control channel is masked with one of thetransmission ID and the reception ID included in the ID pair, and theD2D communication is performed by the transmission operation or thereception operation according to a role determined based on thetransmission ID or the reception ID used for masking the controlchannel.
 37. A method for performing Device-to-Device (D2D)communication, the method comprising: being assigned a User Equipment(UE) pair IDentifier (ID) for D2D communication during D2D connectionsetup with a Base Station (BS) by a UE; receiving the UE pair ID andresource information for the D2D communication on a control channel bythe UE, the control channel being masked with a network temporary IDreserved for D2D communication; and performing a transmission operationor a reception operation to or from another UE determined based on theUE pair ID in resources indicated by the resource information by the UE,wherein the network temporary ID is the same for all D2D connections.38. The method of claim 37, wherein the being assigned of the UE pair IDcomprises being assigned a UE index for identifying UEs participating inthe D2D communication, wherein the control channel includes the UEindex, and wherein the performing of a transmission operation or areception operation comprises performing the transmission operation orthe reception operation according to a role determined based on the UEindex.
 39. The method of claim 37, wherein the UE pair ID is an ID pairof a transmission ID and a reception ID for determining a role of the UEfor each D2D connection, wherein the control channel includes one of thetransmission ID and the reception ID in the ID pair, and wherein theperforming of a transmission operation or a reception operationcomprises performing the transmission operation or the receptionoperation according to a role determined based on the transmission ID orthe reception ID included in the control channel.
 40. A method forperforming Device-to-Device (D2D) communication, the method comprising:assigning a User Equipment (UE) pair IDentifier (ID) for D2Dcommunication to a UE during D2D connection setup with the UE by a BaseStation (BS); and transmitting the UE pair ID and resource informationfor the D2D communication on a control channel to the UE by the BS, thecontrol channel being masked with a network temporary ID reserved forD2D communication, wherein the D2D communication is performed betweenthe UE and another UE by a transmission operation or a receptionoperation between the UE and the other UE based on the UE pair ID inresources indicated by the resource information, and wherein the networktemporary ID is the same for all D2D connections.
 41. The method ofclaim 40, wherein the assigning of the UE pair ID comprises assigning aUE index for identifying UEs participating in the D2D communication, thecontrol channel includes the UE index, and the D2D communication isperformed between the UE and the other UE by the transmission operationor the reception operation according to a role determined based on theUE index.
 42. The method of claim 40, wherein the UE pair ID is an IDpair of a transmission ID and a reception ID for determining a role ofthe UE for each D2D connection, wherein the control channel includes oneof the transmission ID and the reception ID in the ID pair, and whereinthe D2D communication is performed between the UE and the other UE bythe transmission operation or the reception operation according to arole based on the transmission ID or the reception ID included in thecontrol channel.
 43. A User Equipment (UE) for performingDevice-to-Device (D2D) communication, the UE comprising: a transceiverconfigured to perform D2D communication with another UE on a directcommunication link; and a controller configured to control a UE pairIDentifier (ID) for D2D communication to be allocated to the UE duringD2D connection setup with a Base Station (BS), to control reception ofthe UE pair ID and resource information for the D2D communication on acontrol channel, the control channel being masked with a networktemporary ID reserved for D2D communication, and to control performingof a transmission operation or a reception operation to or from anotherUE determined based on the UE pair ID in resources indicated by theresource information, wherein the network temporary ID is the same forall D2D connections.
 44. The UE of claim 43, wherein a UE index foridentifying UEs participating in the D2D communication is assigned, thecontrol channel includes the UE index, and the controller controls theperforming of the transmission operation or the reception operationaccording to a role determined based on the UE index.
 45. The UE ofclaim 43, wherein the UE pair ID is an ID pair of a transmission ID anda reception ID for determining a role of the UE for each D2D connection,wherein the control channel includes one of the transmission ID and thereception ID in the ID pair, and wherein the controller controls theperforming of the transmission operation or the reception operationaccording to a role determined based on the transmission ID or thereception ID included in the control channel.
 46. A Base Station (BS)for performing Device-to-Device (D2D) communication, the BS comprising:a controller configured to control assignment of a User Equipment (UE)pair IDentifier (ID) for D2D communication to a UE during D2D connectionsetup with the UE, and transmission of the UE pair ID and resourceinformation for the D2D communication on a control channel to the UE,the control channel being masked with a network temporary ID reservedfor D2D communication; and a transceiver configured to communicate withat least one UE under control of the controller, wherein the D2Dcommunication is performed between the UE and another UE by atransmission operation or a reception operation between the UE and theother UE based on the UE pair ID in resources indicated by the resourceinformation, and wherein the network temporary ID is the same for allD2D connections.
 47. The BS of claim 46, wherein the controller assignsa UE index for identifying UEs participating in the D2D communication,wherein the control channel includes the UE index, and wherein the D2Dcommunication is performed between the UE and the other UE by thetransmission operation or the reception operation according to a roledetermined based on the UE index.
 48. The BS of claim 46, wherein the UEpair ID is an ID pair of a transmission ID and a reception ID fordetermining a role of the UE for each D2D connection, wherein thecontrol channel includes one of the transmission ID and the reception IDin the ID pair, and wherein the D2D communication is performed betweenthe UE and the other UE by the transmission operation or the receptionoperation according to a role based on the transmission ID or thereception ID included in the control channel.
 49. A method forperforming Device-to-Device (D2D) communication, the method comprising:receiving a network temporary IDentifier (ID) of another User Equipment(UE) for D2D communication during D2D connection setup with a BaseStation (BS) by a UE; receiving information about the other UE andresource information for the D2D communication with the other UE on acontrol channel by the UE, the control channel being masked with anetwork temporary ID of a UE to play a transmission role or a receptionrole in the D2D communication; and performing a transmission operationor a reception operation to or from the other UE based on the networktemporary ID used in masking the control channel and the informationabout the other UE in resources indicated by the resource information bythe UE, wherein the network temporary ID is different for each UE. 50.The method of claim 49, wherein for each D2D connection, a differenttransmission and reception index is assigned to each UE performing D2Dcommunication through the D2D connection, and wherein the informationabout the other UE is transmitted using a transmission and receptionindex.
 51. The method of claim 49, wherein the control channel includesa network temporary ID of a UE to play the other role between thetransmission role and the reception role.
 52. A method for performingDevice-to-Device (D2D) communication, the method comprising:transmitting a network temporary IDentifier (ID) of another UserEquipment (UE) for D2D communication during D2D connection setup with aUE by a Base Station (BS); and transmitting information about the otherUE and resource information for the D2D communication with the other UEon a control channel to the UE by the BS, the control channel beingmasked with a network temporary ID of a UE to play a transmission roleor a reception role in the D2D communication, wherein the D2Dcommunication is performed between the UE and the other UE by atransmission operation or a reception operation between the UE and theother UE based on the network temporary ID used in masking the controlchannel and the information about the other UE in resources indicated bythe resource information, and wherein the network temporary ID isdifferent for each UE.
 53. The method of claim 52, wherein for each D2Dconnection, a different transmission and reception index is assigned toeach UE performing D2D communication through the D2D connection, andwherein the information about the other UE is transmitted using atransmission and reception index.
 54. The method of claim 52, whereinthe control channel includes a network temporary ID of a UE to play theother role between the transmission role and the reception role.
 55. AUser Equipment (UE) for performing Device-to-Device (D2D) communication,the UE comprising: a transceiver configured to perform D2D communicationwith another UE on a direct communication link; and a controllerconfigured to control reception of a network temporary IDentifier (ID)of the other UE for the D2D communication during D2D connection setupwith a Base Station (BS), reception of information about the other UEand resource information for the D2D communication with the other UE ona control channel masked with a network temporary ID of a UE to play atransmission role or a reception role in the D2D communication, andperforming of a transmission operation or a reception operation to orfrom the other UE based on the network temporary ID used in masking thecontrol channel and the information about the other UE in resourcesindicated by the resource information, wherein the network temporary IDis different for each UE.
 56. The UE of claim 55, wherein, for each D2Dconnection, a different transmission and reception index is assigned toeach UE performing D2D communication through the D2D connection, andwherein the information about the other UE is transmitted using atransmission and reception index.
 57. The UE of claim 55, wherein thecontrol channel includes a network temporary ID of a UE to play theother role between the transmission role and the reception role.
 58. ABase Station (BS) for performing Device-to-Device (D2D) communication,the BS comprising: a controller configured to control transmission of anetwork temporary IDentifier (ID) of another User Equipment (UE) for D2Dcommunication during D2D connection setup with a UE, and transmission ofinformation about the other UE and resource information for the D2Dcommunication with the other UE on a control channel to the UE, thecontrol channel being masked with a network temporary ID of a UE to playa transmission role or a reception role in the D2D communication; and atransceiver configured to communicate with at least one UE under controlof the controller, wherein the D2D communication is performed betweenthe UE and the other UE by a transmission operation or a receptionoperation between the UE and the other UE based on the network temporaryID used in masking the control channel and the information about theother UE in resources indicated by the resource information, and whereinthe network temporary ID is different for each UE.
 59. The BS of claim58, wherein, for each D2D connection, a different transmission andreception index is assigned to each UE performing D2D communicationthrough the D2D connection, and wherein the information about the otherUE is transmitted using a transmission and reception index.
 60. The BSof claim 58, wherein the control channel includes a network temporary IDof a UE to play the other role between the transmission role and thereception role.
 61. A method for allocating resources forDevice-to-Device (D2D) communication, the method comprising: requestingresources for D2D communication by transmitting a D2D buffer statusreport or a D2D scheduling request to a Base Station (BS); and receivingresources for D2D communication from BS, wherein the resources for D2Dcommunication is received on a control channel in a downlink (DL)subframe corresponding to an uplink (UL) subframe reserved for D2Dcommunication, or on a control channel using control information formatfor D2D communication, or on a control channel with Cyclic RedundancyCheck (CRC) masked using a radio network terminal identifier (RNTI)assigned to a User Equipment (UE) for D2D communication.
 62. The methodof claim 61, wherein the D2D buffer status report is indicated using alogical channel identifier (LCID) distinct from a LCID which indicates abuffer status report for requesting resources for uplink transmission tothe BS.
 63. The method of claim 61, wherein the D2D scheduling requestis transmitted in Physical Uplink Control Channel (PUCCH) resourcesreserved or assigned to the UE for transmitting the D2D schedulingrequest.
 64. The method of claim 61, wherein the receiving resources forD2D communication on the control channel with the CRC masked using theRNTI assigned to the UE for D2D communication further comprises: sendinga communication request message indicating interest in D2D communicationto the BS, wherein the interest indicates that the UE is interested inD2D communication or in transmission for D2D communication or inreception for D2D communication or in both transmission and receptionfor D2D communication, and receiving the RNTI for D2D communication inresponse to the communication request message from the BS.
 65. Themethod of claim 64, wherein the communication request message indicatingthe interest in D2D communication is transmitted by the UE in aconnected state.
 66. The method of claim 64, wherein the communicationrequest message indicating the interest in D2D communication istransmitted by the UE in a connection setup message.
 67. The method ofclaim 61, wherein the receiving resources for D2D communication on thecontrol channel with the CRC masked using the RNTI assigned to the UEfor D2D communication further comprises: receiving the RNTI for D2Dcommunication transmitted by the BS autonomously, wherein the UEreceives the RNTI when it determines that the UE is authorized for D2Dcommunication based on UE context received from mobility managemententity (MME) by the BS.
 68. The method of claim 61, wherein the DLsubframe indicating resources for D2D communication is different from aDL subframe indicating resources for UL transmission to the BS.
 69. Themethod of claim 61, wherein the control information format for D2Dcommunication is different from control information format indicatingresources for UL transmission to the BS or DL reception from the BS. 70.A method for allocating resources for Device-to-Device (D2D)communication, the method comprising: receiving a buffer status reportor a scheduling request from a User Equipment (UE); determining whetherthe buffer status report or the scheduling request is for D2Dcommunication; allocating resources for D2D communication if the bufferstatus report or the scheduling request is for D2D communication; andtransmitting the allocated resources for D2D communication to the UE,wherein the resources for D2D communication is transmitted on a controlchannel in a downlink (DL) subframe corresponding to an uplink (UL)subframe reserved for D2D communication, or on a control channel usingcontrol information format for D2D communication or on a control channelwith Cyclic Redundancy Check (CRC) masked using a radio network terminalidentifier (RNTI) assigned to a User Equipment (UE) for D2Dcommunication.
 71. The method of claim 70, wherein the buffer statusreport for D2D communication is identified using a logical channelidentifier (LCID) distinct from a LCID which identifies a buffer statusreport for requesting resources for uplink transmission to the BS. 72.The method of claim 70, wherein the scheduling request for D2Dcommunication is received in Physical Uplink Control Channel (PUCCH)resources reserved or assigned to the UE for transmitting the schedulingrequest for D2D communication.
 73. The method of claim 70, wherein thetransmitting resources for D2D communication on the control channel withthe CRC masked using the RNTI assigned to the UE for D2D communicationfurther comprises: receiving a communication request message indicatinginterest in D2D communication from the UE, wherein the interestindicates that the UE is interested in D2D communication or intransmission for D2D communication or in reception for D2D communicationor in both transmission and reception for D2D communication, andtransmitting the RNTI for D2D communication in response thecommunication request message to the UE.
 74. The method of claim 73,wherein the communication request message indicating the interest in D2Dcommunication is received from the UE in connected state.
 75. The methodof claim 73, wherein the communication request message indicating theinterest in D2D communication is received from the UE in a connectionsetup message.
 76. The method of claim 70, wherein the transmittingresources for D2D communication on the control channel with the CRCmasked using the RNTI assigned to the UE for D2D communication furthercomprises: transmitting the RNTI for D2D communication to the UEautonomously when the BS determines that the UE is authorized for D2Dcommunication based on UE context received by BS from mobilitymanagement entity (MME).
 77. The method of claim 70, wherein the DLsubframe indicating resources for D2D communication is different from aDL subframe indicating resources for UL transmission to the BS.
 78. Themethod of claim 70, wherein the control information format for D2Dcommunication is different from control information format indicatingresources for UL transmission to BS or DL reception from the BS.
 79. AUser Equipment (UE) for allocating resources for Device-to-Device (D2D)communication, the UE comprising: a transceiver configured to performD2D communication with another UE through a direct communication link;and a controller configured to control for requesting resources for D2Dcommunication by transmitting a D2D buffer status report or a D2Dscheduling request to a Base Station (BS) and for receiving resourcesfor D2D communication from BS, wherein the resources for D2Dcommunication is received on a control channel in a downlink (DL)subframe corresponding to an uplink (UL) subframe reserved for D2Dcommunication, or on a control channel using control information formatfor D2D communication, or on a control channel with Cyclic RedundancyCheck (CRC) masked using a radio network terminal identifier (RNTI)assigned to a User Equipment (UE) for D2D communication.
 80. The UE ofclaim 79, wherein the D2D buffer status report is indicated using alogical channel identifier (LCID) distinct from a LCID which indicates abuffer status report for requesting resources for uplink transmission tothe BS.
 81. The UE of claim 79, wherein the D2D scheduling request istransmitted in Physical Uplink Control Channel (PUCCH) resourcesreserved or assigned to the UE for transmitting the D2D schedulingrequest.
 82. The UE of claim 79, wherein for receiving the resources forD2D communication on the control channel with the CRC masked using theRNTI assigned to the UE for D2D communication, the controller isconfigured to control for sending a communication request messageindicating interest in D2D communication to the BS, wherein the interestindicates that the UE is interested in D2D communication or intransmission for D2D communication or in reception for D2D communicationor in both transmission and reception for D2D communication, andreceiving the RNTI for D2D communication in response to thecommunication request message from the BS.
 83. The UE of claim 82,wherein the communication request message indicating the interest in D2Dcommunication is transmitted in a connected state.
 84. The UE of claim82, wherein the communication request message indicating the interest inD2D communication is transmitted in a connection setup message.
 85. TheUE of claim 82, wherein for receiving resources for D2D communication onthe control channel with the CRC masked using the RNTI assigned to theUE for D2D communication, the controller is configured to receiving theRNTI for D2D communication transmitted by the BS autonomously, whereinthe BS sends the RNTI when it determines that the UE is authorized forD2D communication based on UE context received from mobility managemententity (MME).
 86. The UE of claim 79, wherein the DL subframe indicatingresources for D2D communication is different from a DL subframeindicating resources for UL transmission to the BS.
 87. The UE of claim79, wherein the control information format for D2D communication isdifferent from control information format indicating resources for ULtransmission to the BS or DL reception from the BS.
 88. A Base Station(BS) for allocating resources for Device-to-Device (D2D) communication,the BS comprising: a controller configured to control for receiving abuffer status report or a scheduling request from a User Equipment (UE),determining whether the buffer status report or the scheduling requestis for D2D communication, allocating resources for D2D communication ifthe buffer status report or the scheduling request is for D2Dcommunication and transmitting the allocated resources for D2Dcommunication to the UE, and a transceiver configured to performcommunication with the UE by controlling of the controller, wherein theresources for D2D communication is transmitted on a control channel in adownlink (DL) subframe corresponding to an uplink (UL) subframe reservedfor D2D communication, or on a control channel using control informationformat for D2D communication or on a control channel with CyclicRedundancy Check (CRC) masked using a radio network terminal identifier(RNTI) assigned to the UE for D2D communication.
 89. The BS of claim 88,wherein the buffer status report for D2D communication is identifiedusing a logical channel identifier (LCID) distinct from a LCID whichidentifies a buffer status report for requesting resources for uplinktransmission to the BS.
 90. The BS of claim 88, wherein the schedulingrequest for D2D communication is received in Physical Uplink ControlChannel (PUCCH) resources reserved or assigned to the UE fortransmitting the scheduling request for D2D communication.
 91. The BS ofclaim 88, wherein for transmitting resources for D2D communication onthe control channel with the CRC masked using the RNTI assigned to theUE for D2D communication, the controller is configured to control forreceiving a communication request message indicating interest in D2Dcommunication from the UE, wherein the interest indicates that the UE isinterested in D2D communication or in transmission for D2D communicationor in reception for D2D communication or in both transmission andreception for D2D communication and transmitting the RNTI for D2Dcommunication in response the communication request message to the UE.92. The BS of claim 91, wherein the communication request messageindicating the interest in D2D communication is received from the UE inconnected state.
 93. The BS of claim 91, wherein the communicationrequest message indicating the interest in D2D communication is receivedfrom the UE in a connection setup message.
 94. The BS of claim 88,wherein for transmitting resources for D2D communication on the controlchannel with the CRC masked using the RNTI assigned to the UE for D2Dcommunication, the controller is configured to transmit the RNTI for D2Dcommunication to the UE autonomously on determining that the UE isauthorized for D2D communication based on UE context received frommobility management entity (MME).
 95. The BS of claim 88, wherein the DLsubframe indicating resources D2D communication is different from a DLsubframe indicating resources for UL transmission to the BS.
 96. The BSof claim 88, wherein the control information format for D2Dcommunication is different from control information format indicatingresources for UL transmission to the BS or DL reception from the BS.